Mexc Global is a good exchange, but there are other exchanges that are having good services too. If it is no KYC exchange, there are still some too, like Kucoin.
You make profit from trading, not because of the exchanges that you you are using.
I will advice people not to trade with many altcoins because altcoins are like gambling. If they go in the direction that is not favouring you, it would be a big loss.
Very correct there is no exchange that you trade in and get automatical profits from it, success in trading has to do with the level of knowledge from the trader and also good timing, also the availability of trading pair on the exchange for traders to trade.
In terms of trading actually you can choose to go for decentralized exchange or centralized exchange it's all your choice, but I am always going to go for decentralized exchange to trade.
Here is a list of centralized exchange and decentralized exchange you can carry out your trading activities.
https://bitcointalk.org/index.php?topic=2906237.msg29885570#msg29885570