Bitmex was good I use it but their trading volume sucks not only because of regulations but also they are not improving anything on their platform- they keep adding shitcoins to trade futures thinking it will bring revenue rather than focusing on UX friendly design.
BitMEX does not upgrade their UI/ UX too often but if you only want to trade Bitcoin in futures perpertual, trading volume on BitMEX is good enough.
You must be a whale with very big trading capital to feel trading volume on BitMEX is not enough for your position to open and close.
That exchange has one dangerous thing you must know.
Bitcoin Flash Crashed to $8.9K on BitMEX. This crash on BitMEX happened three weeks ago and you must be careful with Futures trading on it because of liquidation risk.