Most of the time I don't really mind if the base was the artist's or not. However, I think that, when the base was made by the seller, the value becomes higher, because it's something purely made by own hands if you get what I mean. It's extra-work and they deserve a bit more worth.
The design's important but using a base can cause a limitation in design and looks kind of lazy. I guess it's kind of like shining up your product before you sell it. I think it's okay to use a base as long as you don't let the lines restrict the design but I think using different poses and what not helps.
I look for unique adoptables most of the time, like batches of monsters or something, even when I dont buy them, so it makes sense that I don't care much for the ones made on the same base or lineart. I wouldnt mind if I was more interested in normal animal adopts I guess (cuz theres a ton of animal bases and linearts) but since I am not into them I really dont care.
I find it doesn't really bother me when someone uses a base that isn't theirs. Unless they "abuse" the base (say it's a cat base, but they add dragon wings, different eyes, horns, and change the shape of the base a bit), I'd rather they make it on their own.
tbh I don't buy adoptables bc like I have enough strange animal things lmao but I think it's better if they at least make the base themselves ?? Or at least use something that the artist has given permission to use for making adoptables bc otherwise they're basically using someone else's art to make money
I don't mind, but adopts made with a base shouldn't have a price higher than an unique lineart. Basically with an unique lineart you're also buying a flat/reference of the character that was made for you only.