As others said, there should be one listing per base, to eliminate the noise.

Take an instant to look at a practical solution that already exists in VRchat:

(pic 1) Drop-down menu of "AvatarNow" from avatar museum

Showing the base (and base's author name) as the main listing,

then either a drop-down of variations (dedicated collumn on the right?)

or a dedicted page showing listings of duplicates,

would not only reduce the noise on main listings but potentially allow separate creators to work on a same base.

As for concerns over "others working on a same base" let take another example: (pic 2) Holoearth's player economy

When people make clothing based on liscenced characters, they purchase one as part of the process to make the listing.

Here, to post a variation on an existing base you could have something similar so the original author gets a little something off people using their base in the marketplace.

The idea of adding one layer of depth to the menu may seems annoying at first, but when someone click on the base they want they are already focused on browsing for this product in particular.

I don't think they would be too annoyed with the menu transitioning to a form similar to the screenshots full of duplicates others sent

IF it is within the context of browsing variations after selecting a base.

The current problem mostly is in the context of too much noise being created around main listings, which is a different scenario.

Multiple variations of the same avatar should all be under one listing. Moreover, if it's just simple color changes, the avatar creator should be encouraged to integrate that into a single version utilizing the avatar's expressions menu.

unsure who this image is from, but it is a prime example of this issue. the same avatar with minor texture changes being listed seperately leads to significantly reduced ux