Definitely, it is getting worse and the probable causes are

• We are running out of interesting topics to discuss.
• Newbies trying to teach how to be an expert.
• Merit sources ignored primary discussion boards because it's mostly filled with spam.
• Veterans left the forum for multiple reasons.
• Missing reporters like Actmyname.

What we can do to make it better, ban signature campaigns completely It will effectively stop the posts that are created to meet quota but it reduce the traffic into the forum drastically.

So we need to accept the fact, that BTC is what it is and we can't expect the information to be new in every post we post, merit sources should also have to look at the primary discussion boards and encourage posts that contribute something to the discussion which doesn't always necessarily to be exceptional, long and technical.

You are right, after the ban of mixer many members have shifted there time and devotion to other forum ALTT so the quality there increased more then it decreased here. I think you are also there? Spending time here and there is not so hard but it affects the quality of the post. Besides this factor, posts on this forum are depend on the nature of the market. If its the trend of ETFs, then you will see relevant discussion. If its war, casinos, SEC, or seizure etc. whatever is being discussed on trending is being discussed here.

So, I won't say the quality has decreased, its just more newbies are coming day by day, some are spamming, and the remaining ones are not so active here with good topics I don't know why? Besides speculation threads, I only find good readable thread on development section of BTC or in local board. BTW what you think, is not being discussed here, or what should be the main goal of posts or what types of posts are not seen anymore here?

I agree in a sense.  Clearly this forum has taken a massive and steady decline since 2016.  You'd have to have your head in the ground to think otherwise.  I disagree wholeheartedly with your assumption that it has anything to do with the mixer ban though.  Mixers were paying people to come here and spout nonsense while defending each other's bad actions to the point the trust network is a joke.  That led to users attacking honest people who build things here, so actual useful members just take their talent and leave rather than bicker with idiots who are only stating nonsense to get more posts in and earn more.  Now that these paid to post troublemakers are starting to leave here, it's almost becoming bearable to have discussions and build on ideas again.  Maybe we'll see something of value built here by the community again at some point rather than leaving Bitcoiners to chase Ordinals and Runes for something to do.

When I joined this forum in 2022, the chipmixer campaign was still open, and there were so many legendary members who were creating many educational threads. The discussion on the forum was really great and eductive for newbies, but after the chipmixer campaign ended, I felt there was a little bit of a decline in the discussion. 

Most of the old, legendary members I know were mostly talking about Bitcoin privacy and security, but since mixers got banned on the forum and people are not talking freely and adding links to mixers without being word-filtered, I think that's what makes some people just lose interest too. 

Leo was really a reputable member that likes privacy and talks about privacy mostly; if he were still here today to see that mixers are banned on the forum, I wonder what he would have said. 

I know that this forum has not really become worse as some people think. Currently,  members are just sharing the knowledge they have, and most of the people who have already left or stopped being active were members who actually had a lot of quality knowledge about Bitcoin, tech, and development compared to so many of us here. 

Wouldn't say that forums is getting worse, it's just getting boring. Wouldn't relate it with mixers ban because I noticed such trends long time before it. I only see ban of mixers as first signs of censorship.
Main reasons already mentioned. Most of things were already discussed already so many times that's difficult to find new topics to discuss. Technical things were already discussed a lot and it's thing not for everyone.
Many old time members who made this forum iconic already left forum for various reasons. Without them Bitcointalk isn't same. Another reason is Bitcoin and crypto turning into mainstream thing, previously lot of discussion were about how to introduce crypto to people and business.
I already miss old times when we have never ending drama in Reputation board or annoying trolls posting from alt accounts .

It'e easy to find reasons to ban casinos there. You probably know that most of them is registered in offshore countries like Curacao. They're not paying taxes in rest of countries where they're operating, they not always following all local regulations. Also, I guess fiat bookmakers also aren't very positive about their competition. If governments would start taking actions against them, theymos wouldn't have no other choice than banning casinos, same like he done with mixers.

Sure, I don't mind the idea of making the forum "better" so long as it doesn't change the look and layout. Why?, you may ask. Because when people come here to read satoshi's old posts, I think they would prefer to read them in the same format in which they were written. It lends more credence to the idea that they were actually his posts. For me, this is where the true value of the forum lies.

If anything, I think it would be neat to be able to design a mobile version of Simple Machines Forum from scratch, from the ground up. It is true that most internet traffic is mobile these days, and it ain't so easy to read the forum from a mobile device.

Many people think facebook (which I stopped using more than 10 years ago) is completely crap compared to what it was 15 years ago and they are right about it but there is a difference between facebook and bitcointalk.

Facebook is always changing stuff. Changing the UI, changing-adding-removing features etc. bitcointalk has only made a few minimal additions (like the merit system) in the last 10 years and that’s actually one of the features I like about btt. I don’t like websites that change their look all the time.

If there is one thing I like about btt, it is how it kept its current look. I probably won’t like any changes they’ll ever make and I still use the old.reddit for the same reason.

I can’t say what I want to say about facebook. I will say the scroll is terrible.

They said that you won't know what some people's have contributed to this forum until after they have left, and when some of the people's stated that, I was not believing, but now I'm 100% agree with that. Because since the time they banned those mixers, this forum just hasnn't attracted well, unlike before when the mixers still existed in this wonderful forum and everything was moving steadily. Now,  if we look at this forum, there's a lot of good topics, like before, when everyone only chose and created any thread they wished.

But if I may ask, are only those mixers that have contributed good threads for this forum? Why I am confused is that after they get banned, they are supposed to continue from where they stopped and begin contributing better threads and the importance things that this forum deserves, but nothing like that is the only thing that has been surprising me about this forum.