While hiring, do you really care about a candidate’s frequent job switch or just skill set?

Anything less than 2 years will raise questions, be it something because of you or the company. Ideally, no company would want someone who switches frequently. It will take ~1 year to get going. If people switch around that, they need to bring in new people and start again, which is a lot of efforts and waste of resources

Skills are indeed part of the equation. However, for frequent job switches like every 6 months, it may spark a few queries. But exceptions do apply in certain circumstances. Reputation, role suitability, cultural fit, and adaptation capacity are some additional considerations. While duration isn't singularly critical, when persistently brief, it constitutes a black mark.

I do. If someone has been switching jobs in one year or less at most companies it is symptomatic of someone who doesn't get along with coworkers or is terrible at their job

Also you don't really learn anything in terms of "experience" in the first 3-6 months at a new company... depending on role and position. So mentally I deduct that

It depends. In my case, I was interviewing for senior developers who can actively maintain and take the current codebase forward (eventually lead) which was already serving multiple applications.

So it would have taken at least 6-8 months to become comfortable with the same. If you are constantly changing orgs in a span of year that will prove costly for the team cos of all the training and process one is involved with.

Obviously, skill has still much more weight than this and job switch only accounts for maybe 15% of the decsion making process.