Verpets is dead? Heck, I used to work for them back in 2015-2017, produced over 200 assets but eventually had to quit.
The problem with petsites is... I think, one of them is the art style. You mostly either see hyper-realistic horse breeding sims, or cel-shaded, cartoony, clearly neopet-inspired graphics. For the petsite to hold on a little longer, it needs to be something new, something that "pops". At least in my feeling, I can't bring myself to try any of these out, if the visuals aren't appealing to me enough. It's been done, over and over. Or, the sites don't have a defined style and just throw multiple styles and a mixture of random creatures at the player as if they didn't know where to go with the core concept.
Dragon Cave can be considered ancient as it was launched in 2006 and is still going strong. It's a simple "raise and collect" pixel dragon game with monthly releases. The sprites are kept in a somewhat realistic style, detailed and well executed. They're unique in that matter. The dragons never die of old age so you keep your pretty collection forever. It's free-for-all, no pets behind paywalls, no premium currency or other microtransactions, the only time you may choose to pay is to get rid of ads, which aren't invasive either.
Flight Rising is also one of the petsites doing extremely well as it offers multiple gameplay mechanics, pet customization and, again, unique art style - which is very vaguely inspired by neopets (e.g. your dragons have pets on their own) here and there, but is not a direct copy of that style. I just came back to it after a long break and was greeted with dozens of updates and improved mechanics. Sure there's a premium currency but you don't need to pay a single cent, you'll mostly get those from trades!
And lastly, Lioden, among those real animal sim sites, stood out for me the most - one, there are no other lion sims out there. Two, its gameplay is based on real laws of nature, with twists here and there. This, mixed with just as realistic art-style, makes a unique experience. Sadly I quit because I don't like the idea of my virtual creatures dying from old age, haha. That's just a preference of mine.
I don't know any more petsites that stood out for me, they're alive since forever and made me stay; either the style was same-ish, simply unappealing, or not enough gameplay, or badly executed paywalls. Or terrible communities.
where are the birb sims at