Is it still possible to get a decent job in academia (specifically physics) nowadays? I am an American high schooler considering what to do in university. I am immensely interested in theoretical physics, and I would quite like to become a professor in the subject (I've self-studied quite a bit of it; while I'm no master, I can still do enough to have a decent bit of reputation on the Physics S.E.). However, I've been hearing some rather concerning things from others already in academia about becoming a professor in physics in particular. First of all, I've heard here that every new crisis is permanently harming the job market in academia overall. Secondly, I've heard in several places (including here, if I recall correctly) that the job market for new mathematics professorships is starting to dry up, which most likely means the writing is on the wall for physics professorships. I've heard plenty of personal anecdotes from friends who have parents in academia about how brilliant folks who went to top class schools are now either not able to find work at all or only able to find work in small, relatively unknown universities. Finally, I've heard from a couple physics professors and chairs that it's somewhat difficult to find a first position in physics in general (though it is apparently relatively straightforward to achieve tenure once you get your foot in the door, so to speak).
I've really enjoyed my self study, and research seems quite lovely with the little experience I have with it. Thus, I'd really, really love to grab a PhD in physics and teach and research for the rest of my time here on this planet,  but I'm concerned I'd be left out without a job if I tried to do so! Is my outlook on the situation too bleak, or would I be right to travel a different path and perhaps research on the side?
I've heard from a couple physics professors and chairs that it's somewhat difficult to find a first position in physics in general

This is a dramatic understatement. I always recommend reading the first chapter of Karen Kelsky's book. She demonstrates that our universities are not in crisis -- that was 20 years ago. Rather, they are in decay. Most departments are not growing; they are shrinking and cutting back. Yet, graduate programs keep pumping out PhDs.
For physics in particular: APS reports that in 2012, 1800 physics PhDs were awarded. In contrast, there are 9400 physics faculty positions total -- about half of which are at institutions with no physics graduate program (i.e., schools that -- with a few exceptions -- focus on teaching rather than research). From this, you can estimate what fraction of physics PhDs end up with faculty research + teaching positions (see also here).
In short: saying you want a faculty position is like you saying you want to join the NBA -- of course you do! But even for the best students, it is a long shot.

I'm concerned I'd be left out without a job if I tried to do so

Now for some good news. 1-year post-PhD, only 4% of physicists are unemployed. The overall unemployment rate for those with a physics PhD may be around 1-2%. There are research positions outside of universities, and there are also non-research positions that are both intellectually engaging and financially remunerative. Further, you should not have to incur debt to attend graduate school. Thus, attending graduate school in physics might be a good choice (financially and otherwise) even without the allure of a faculty position. But it is certainly good to be realistic about the situation; indeed, you might consider subfields, projects, and skills that could lead to interesting work both inside and outside of the university.
Note: this answer, and the statistics therein, refer entirely to the situation in the US.