Do you feel this is a detriment to the market and industry, or just a way things are?
I wouldn't think so? I mean, I haven't really seen any sort of negative impact, despite most games I've seen not really caring much for the "pet" aspect of their game. I mean, before Neopets added in the clothing feature, their pets were even more in the background. People got them just to use the pet pages, but it was still successful and the idea of pet sites still resonated with a lot of people, resulting in the continuation of the genre today.
I think the main thing to keep in mind for those wanting to build their own pet sites is for them to ask themselves, is it a pet site they want to build? If there are pets, how necessary is it really for them to be there? Is there any purpose to them? If it's not the focal point, like Subeta, calling it an "avatar" site would seem to be more appropriate and advertises much more what the game is about. It's kind of like having genres for books or movies, I suppose? Helps people identify what your game is about. If you call it a "pet" site, people are going to expect the pets to be more than eye candy you can leave starving and bored.
Though then again, /because/ so many sites have used the term "pet" site, despite the pets being an almost nothing feature, we've built up this understanding and expectation of what pet sites are. Nowadays, we expect a site called "pet" to be where you can just completely ignore the pet features, and the main attractions are everything else.
Even with people trying to think of new and innovative features for pet sites, whenever I see these discussions come up, almost entirely they're talking about features /other/ than for the pets. Like crazy explore systems, certain integrations with mini games, etc. It's a bit comical, really. People are coming up with great feature ideas for a pet game that don't at all involve the pets XD (To be fair, occasionally there are mentions of battling, and once I did see someone have a fantastic renovation for the standard feeding system, but nevertheless, it seems like building crazy awesome new features that involve the pets are basically not even considered to begin with.)
And just to be clear: I don't find this all to necessarily be negative nor am I necessarily in disagreement with how sites are run/developed.