It has been a while since I set foot in a gym, but the 3 gyms I have used over the years would be awkward in the covid era.
Changing rooms, gym equipment, ventilation and layout were all unsuitable and would require major alterations.
And I fondly remember the over-diluted cleaning fluid that we were all supposed to use on the machines, to wipe off our sweat. I think I may have been the only member to ever use the cleaning stuff, and when I did I had to trek to the ladies loos for toilet paper to use as a wipe. lol. The gym staff were (apparently) told not to refill the paper wipe dispensers in the gym itself, because then people used them, and that was too expensive.
No one (including me) ever wiped the handles of the equipment.
Exercise classes must be disease breeding grounds, with all that panting and sweating and jumping about.
I suspect that a great many gyms will be going out of business in the near future, especially since many people will have discovered that they can keep fit perfectly well from home, without paying the exorbitant monthly fees.