Hard to say, but logically thinking it should have improved sales with people being stuck at home.
Well from a production standpoint, I don’t think it should be too bad a hinderance.
Since it’s all done on a personal computer: the writing, artwork, and music can be done from home. Meetings for exchanging ideas via online sessions. For recording voice acting, they can schedule one person in the booth at a time, then do hard cleaning to sanitize the place for the next individual. COVID doesn’t survive on a non-organic surfaces for more than 72 hours, so they can also have people only go into the booth once every three days. Some voice actresses might have their own home setup for recording audio, in which case, they can do it from home.
I imagine the worst impact would be store purchases. I’m not sure what percentage Japanese eroge fans buy physical over digital, but seeing how stores stock up on inventory, it seems pretty high. Physical copies tend to have all the “limited edition” collectable stuff.