I don't think you've quite elucidated the real danger to thinking here.

I agree that mediocre thinkers pose a danger to your quality of thinking. But your advice is all about how not to adopt other mediocre thinking and/or to think better oneself.

That's not the danger. The danger is that when you are in the company of friends who are mediocre thinkers, and you say something that is poorly thought through, they lavish you with likes and snippets of praise anyway.

This makes you feel that you've done a good job, when in fact you've do a mediocre job. It trains you to embrace mediocrity.

Furthermore, when you debate people who are mediocre thinkers, and you expose the glaring flaws in their logic, they often will not have the wherewithal to expose glaring flaws in yours. Your rhetorical victory makes it feel like you're astute and canny, when really it's again just reinforcing mediocrity.

So, yes, engaging with mediocre thinkers does make it difficult not to fall to mediocrity yourself (or stay mired within it if you've never done better). But it's not mostly from being star-struck by influencers or wowed by credentials or being incredibly gullible or being unable to think at all. Rather, it's from low standards.

And the way to resist is to hold oneself to high standards, and to seek out discourse of the highest quality when one can.