Wow, from the times i traded (got rekted) on bitmex i completely identify with alot of what you are saying, weird behavior, orders not executed, poor control on the margin and violent manipulations (spikes) in the most abrupt price changes in comparison with the actual price, maybe they weren't so organic.
Time will tell, but you are correct that we are better off with regular trading or simply hodling, but alot of people are being misled in their trading if this is true.