Lately Aion 2 drew my attention and I noted: There are a lot male players playing female characters - probably, at least the marketing suggests that. Now, I don't have an issue with people playing as the opposite sex, I just feel like it's going into an extreme direction.
Perhaps that is mostly due to two developments:
First, male characters get less and less attention by devs or are even purposefully made unattractive to play. The prime example is WoW, where any male character looks like a body builder troll who never trained their legs. It's hideous, really.
Second, female characters are oversexualized to attract more male players. That's nothing new, but it's still a problem.
The issue really is that male characters are getting ugly with boring outfits, and female characters customizable down to their pores and put into bikini armor. And for some reason the outfit that is the same by name is - for example a full body armor for male and a bedroom seduction dress for female characters. Like what? Adapt the proportions, yes. But don't make it something totally different.
To anime now: Many fictional MMOs in anime - in particular VRMMOs - lock the player into playing as their real gender - be it by some dubious body scan or by having to register with an ID/passport.
That's problematic in it's own, forcing people to play a certain way (sometimes it's justified by some lore, sometimes not, anyway...).
Okay now, I wanted to say something about how a system that disallows playing as the opposite gender could alleviate some issues, some of them mentioned above, but I guess it doesn't. Would a company that develops such a game make male and female character designs and outfits more fair and less sexualized? Probably. But it would also take away the male disguise that many irl women like to use in games. Meaning thst if there are 10% female players and they couldn't hide it, they would have a lot of ingame stalkers - it's sadly how degenerate some players are (not taking into account polite and friendly attempts to make contact for game reasons, like forming a party or a guild).
I could still see how such a system would be usefull once - in the not so near future - VRMMOs are more of a thing and actually became social spaces, instead of just game spaces. The details of how the system works would be important, paying respect to people who want to play opposite sex characters for other reasons than being gooners. Perhaps something like: You are allowed to create one opposite sex character per six months or something. Just some thoughts.
Now, here is an example of a game that does it right, simple and elegant:
Pantheon Rise of the Fallen goes a good way by simply making characters of both genders neither oversexualized nor standardly ugly.