ive been lurking around this site for a few years now, but this post made me feel obligated to make an account because its clear to me your team has put a lot of love into xanje and id hate to see it go the way of other pet sites.
so for starters, i agree with the others that the landing page likely plays at least a part in it, but i dont think it has to do with the menu being to cluttered at all. when i personally visit a pet site, seeing the menu gives me a quick idea of what to expect and i like sites that let me poke around a bit without requiring an account. plus i think the images on the front page that display the different aspects of the website helps build interest.
my main critique of the landing page would have to be the "welcome to xanje" image. the art isnt bad by any means, but it looks a bit outdated when compared to the rest of the site's art. i think an update to that wouldn't hurt either
as for layout, i think having a nice header that looks distinct from the reat of the page could REALLY help modernize the look of the site. right now it gives me geocities vibes with the singular background image, and although that doesnt bother me personally, i think it could turn new users away. i would suggest looking at sites like flight rising, dappervolk, or tattered world for general page layout ideas. but overall i think a separate header with a different bg image could do wonders for it.
content wise, i think most of the site is fine. although, just going by what draws me personally into starting on a new petsite, i've always liked the ability to dress pets up. color combos can only go so far to make your pet original, IMO. khimeros has a system for static images that can be overlaid and resized to fit with a particular species, so i think if you did go down that route, this particular method would make it easier on the artists so they wouldnt have to draw the same image for every single different species. if not that, you could also look into allowing users to customize their pets by drawing over top of them a la Dappervolk.
also i think it would be nice to be able to breed different species together and get an assortment of both as offspring, but i also understand this could potentially cause lore/worldbuilding issues so i wont press that, its just my preference. i like the surprise of not knowing exactly what I'll get.
one thing that confused me, though: i bought a butterfly firedrake, and a rainbow lava firedrake. i thought id be able to breed them together since they were both firedrakes, but that isnt the case, it seems. i think, at the very least, all of the same soecies should be able to breed together. you wouldnt have to make hybrid designs of them, maybe just have a random % chance for what pattern you get, like how in FR if you breed two diff dragon species, the more common species is the most likely offspring outcome.
sorry if this is really ramble-y, and feel free to message back with any questions, i just felt like this was an area i could contribute to, as most pet sites dont have a lot of staying power for me, and FR, DV, and neopets are about the only 3 that have been able to consistently keep my attention. i think the pet customization and worldbuilding has a lot to do with that