It doesn't matter how large the market cap is. Bitcoin defined itself as a currency - currently, it is a very limitet one. Very far from being mainstream for a currency. For an asset? Sure it is mainstream. But bitcoin defined itselt (at least, satoshi did) as a currency - not an asset.
If you talk about Bitcoin as a mean of payment, then I agree with you, it's not a mainstream and will never be because it's not designed for that. Bitcoin was created to simply get rid of 3rd parties and create a decentralized, P2P transaction in ecommerce.
To be honest, I think that Bitcoin was most likely a test project than a final solution to the problem that Satoshi wanted to solve. There are 7 billion people in the world, 5.5 billion of them have access to internet and Bitcoin's block size is 1 MB. It's impossible for Bitcoin to become a mainstream currency because 1 MB block size is the limit. For it to become mainstream, we need to change it's protocol, so still, I wouldn't say that it will never become a mainstream because it can, we only need to modify things.
I agree with you, but I do think the original goal of bitcoin was to create a mainstream payments system.
About the block size, it's not only that. As transactions/userbase grows, the operation cost (I mean, more miners will join as bitcoin becomes more and more popular) grows exponentially. Proof of work just doesn't scale well.
Maybe I'm wrong, and satoshi did create this as an inital proof of concept.
Bitcoin will most definitely become mainstream at some point. I know firsthand that Apple executives have been stacking behind the scenes since at least 2018. It is only a matter of time before Bitcoin is added to ApplePay, at which point many people will be able to stack and simply use it without even knowing anything about it, the network, or self custody.
You are considering off-chain centralized transactions. But the whole point of bitcoin is to be decentralized. If more people adopt bitcoin as an asset and it becomes mainstream, but only using these payment apps controlled by big companies, it really isn't bitcoin anymore.
You said Bitcoin will never become mainstream, but I regretfully disagree, it's okay for me not to agree because it has already become mainstream, many people use Bitcoin today because of the many benefits it brings.
Such as freedom, decentralization and transparency.
And thus, they escape inflation, by using fiat money, your money only melts away with inflation, this is the real issue to discuss.
True, inflation is a real issue.
To clarify, I'm not against bitcoin or what it brings to the world. I just think that won't be mainstream. Not that i don't want it to be.