Also Mega Evolution in general. I dislike most of the Mega designs and outside of the 3 stage mons that got them, they really felt like a message that the single or two stage mons that got them were going to be locked out of a possible future evolution down the line. Now, there's no confirmation this is actually the case, but it feels way less likely now that they'll make, say, a Lucario evolution in the future or a Sableye evo.
Lucario is one of those Pokemon that I don't think needs an evolution and nor can I envision a normal Lucario evo to begin with.
It's insanely marketable and popular by itself which is one thng, but as a whole this is one of those cases where even though it's a two-stage line, Lucario feels pretty "complete" in my eyes. It's a Pokemon that's so perfect as it is and I couldn't ask for more from it, and that's my DP kid bias speaking partially I admit but I don't think it ever needed anything, but a normal evo is the last thing I could ever envision for it.
While I love three-stage lines, especially those outside of starters and pseudos, I think some single stage and two-stage Pokemon are perfect as they are and don't need to be expanded. Heracross is an example of a single-stage Pokemon I like and which feels very complete.
Sableye I admit is a bit of a bummer, since it's pretty terrible on its own in battle, but it is what it is there.
I also believe they prioritize worldbuilding over giving anything buffs on purpose, whether it's evos, Megas, or regional forms or whatnot. Some Pokemon are just not meant to evolve further in Game Freak's eyes nor do they have any intention of giving them an evolution. And as much as I love cross-gen evos, that's also okay sometimes.