Ethical breeders don't sell to pet shops.I think you could have a thousand good breeders, but people will sadly go for the cheapest option, because anything that involves more care and a better environment costs more and eats away at the profit. I think, instead, regulations need to change for pet shops.
I ended up getting my two boys from Pets Corner (can I mention the shop’s name?). They were slightly older (around 12 weeks, and had been together as a pair from the beginning) and they were the only guinea pigs there. I was told that they would not have any new pigs until they had sold the ones they had (words were actually "until they had a home"), whereas at P@H, in contrast, I was told that any leftover/slightly older/single guineas were put in the adoption centre when new stock came in. The guinea pigs at P@H were also in large groups, so you weren’t guaranteed to get two that liked each other (I’m also not sure if I misheard, but they’re also only sexed when they get to the store?).
I don’t know how much weight to put on it, but Pets Corner states that they only get their animals from “ethical” breeders who meet their standard and adhere to their contract (which I read and really hope is followed). If every other pet shop could do that, it would certainly be better for the animals. I also wasn’t allowed to have my two until I’d actually shown some form of proof that I had everything (right down to whether I had hay, a run, and food); the health check they went through was also very thorough. Contrast that to P@H where I saw someone get guinea pigs who had no idea what cage they needed, why they couldn’t live alone, and surely you could mix two from different cages together?, etc., etc.
I think it’s not just about breeding, but also about somehow ensuring that they go to the right homes. You can breed to improve genetics and health, yes, but if that animal still goes to a home where it's not going to get the best care, what then?