◇ Could this help me?
Yes, and the framing is more honest than most tool recommendations. Design skills work for a mundane reason: an agent with no design direction reproduces the most common patterns in its training data, which is exactly what the generic look is, and a skill supplies the direction that was missing. The creator is a design lead and says plainly that this gets you to good enough rather than to good, which is the right expectation. The third recommendation, checking against accessibility and usability guidelines, is the one most people skip and the one with consequences beyond appearance. General practice, with the standard caution that each of these is installed instruction content from a third party and worth identifying and reading before approval rather than installing from a comment thread.
I want to compare design skills properly rather than installing all of them. First, for each of the candidates I name, tell me the canonical repository, who maintains it, what the skill actually instructs, and what files it reads or writes, and install nothing until I approve it. Then set up a fair comparison: use one fixed brief for all of them, build the same page with each skill in turn, and show me the differences in layout, typography, color, and motion side by side rather than describing them. Finally, run the result past accessibility and usability guidelines and tell me what fails, since that is the part I cannot judge by looking.