I strongly believe exchanges are playing a negative role in the space, mainly because of price manipulation. And if -like in any society- evil doers are not going to pay a heavy price, we all stand a lesser chance to succeed in our investment.
I also believe cryptocurrency exchange site have an impact in the reason Bitcoin is not mainstream now but it not through the act of price manipulation you said because thats the role played by the whales and arbitrage traders. However, exchange site are only guilty of fake volume and liquidity.
There should not be a possibility for someone to short or long a crypto, sell or buy, unless he really holds it!
Binance and some other exchange offer this service and I think some problem are caused by naive people in the crypto system.
I watched this debate between Peter Schiff (Gold bug) and Anthony Pompliano (Bitcoin bug), a rare piece of what you call a high quality debate that you could barely watch these days:
https://www.youtube.com/watch?v=Wigz8z6Vm3UIn this debate, Peter Schiff said yes his company lists Bitcoin as a payment option but they don't accept it themselves, they have instead a payment provider called Bybit that pays them in dollars. Which makes Bitcoin of course more expensive to pay with since you now have a middle man.
And I think he's right in not accepting Bitcoin. Exchanges would pump the hell out of Bitcoin, dump all the bitcoins they could possibly have to buy gold and then let the market return to its normal place again.... This of course plays against Bitcoin mass adoption.
Anthony Pompliano is genuinely a crypto enthusiast but Peter Schiff accepting crypto payment through a third party is still since he seems to be less experienced about crypto payment and how to stop loss but he claiming exchange site pump and dump bitcoin is just an excuse.