This is an important question I think, and it's too bad that it's not getting more traction here.
If you are doubting your capability ... don't. You are capable of this, period. You know the drill: study Sedgewick/whomever, do LC problems, make sure you understand graphs and DP, etc., etc. The interview process these days is bullshit, it just is. Build those interview muscles.
Also, make sure you properly are managing the usual life stuff: diet, exercise, sleep, meditation, etc. Don't discount those factors.
Now, that said, if you are questioning whether spending the next 6 months of your life studying algorithms -- or, for that matter, the next 30 years of your life doing the software engineering hustle -- is the best way to spend your time/life/energy, that's a very important question, and I can relate. Time spent doing one thing is time you won't spend doing something else. You have one life to live and you have to get real with yourself how you want to live it. If you eventually pivot, OK, but pivot thoughtfully, and for the right reasons. But I don't think you should make the mistake of thinking lack of capability is a factor here.