I don’t think it’s children’s properties being intended to sell toys that drives this. It’s WAY cheaper for the production company to shit out crap with talking dogs that kids will watch than to hire the level of creative team and fund them to make the same number of episodes but good art.
it's all of the above you can make a show purely for the money and to increase that profit you can cheap out on production costs and trend chase to save time the real $$$ in TV was and still is merchandise, though - most of the big 80's cartoons looked at fondly were >95% designed to be toys first