I think there's lots of opportunity for good CPAs. IMHO, though, you don't want to do what solo proprietors have done in past.
E.g., easy 1040 returns? No profit in that due to TurboTax. And monthly write-up work (aka "bookkeeping")? I think that is a really tough nut to crack because most users want to "do" QuickBooks themselves.
So what you want to do is focus on more complicated stuff that untrained people can't do themselves. In tax, that means corp and partnership returns, multistate taxpayers, people with international tax issues. This stuff can't safely or optimally be done on a DIY basis. (Look at how often the Bogleheads DIYers get these things wrong...) So do this more complicated stuff, and you can do great.
P.S. If I was in my 20s instead of in my late 50s, I'd think about working with a small firm or solo practitioner who is doing a practice "right" and then position myself to be her or his successor. Lots of risk of the relationship not working out, of course, but the profession is getting older and lots of CPA firm owners need to find a successor.
Putting this all into FIRE terms, learn some retiring practitioner's business... buy her or him out on a short-term note (using profits to pay off the note very quickly)... then decide if you still want to FIRE ASAP or if you maybe want to work a few more years (rapidly growing your net worth).
P.S. I didn't feel comfortable going into any more detail about the MAP data, but within that group of "A" performers, there's the same sort of wide variability in profits too. There's a big difference, e.g., between A-, A and A+ performers.