What is the top 10 exchanges which all the investors trust it?
For me
https://www.coingecko.com/en/exchanges is providing the best list of the trusted exchange site with actual volume without the manipulation that created by the marketcap site itself. coingecko is better than CMC.
There was a trust score method that can determine the best exchange site. You can get it on the cryptorank.io too.
I wouldn't trust that list too much. It has Poloniex listed on 5th place with a trust score of 10. It started to decline since it was sold to Circle. I wouldn't give it 10. Poloniex is having issues and is not going to survive on thsi market without major changes.
Also many of the listed exchanges are local and popular in certain regions like China. Some allow US citizens some don't. It's hard to say which exchanges are the best worldwide if you don't have access to them from your country.
You are right recently many exchanges changes policies and now many fake trading volumes and with too much issues even crypto related exchanges never give priority to support now most of them are change in shit exchanges once I have issue with poloniex and submit ticket then I have to wait for 2 months then reply came and this was not complete its really poor marketing by them.