CFOP has many extensions, but then so does ZZ. They cancel out.
ZBLL is too many algs, but it isn't. You can definitely learn all minus sunes and anti sunes in a year.
XEOCross/EOCross+1 is amazing but pretty difficult and is slightly less work than seeing cross+2, but when done it is amazing. It is also possible about 50% of solves imo.
Blind spots in ZZ are a thing but not really because EO is solved. This means that you already know half the information of any edge on the cube. You also get blind spots in CFOP, so again, it cancels out.
With EO being solved, it's even easier to optimise F2L because you have half the number of cases. This means that tps can be even higher.
ZZ hasn't got a lot of users because it's bad is the wrong way of looking at it. ZZ is currently slow because it doesn't have a lot of users. I know of 2 other ZZ users in my country. That's compared to the several hundred CFOP users and around 10 Rouxers. ZZ has little to no chance of being picked up by some fast kid compared to CFOP.
The argument about why haven't fast people switched has 2 solutions:
- They are already sub 8 with CFOP so why put in loads of effor for something that would mean that they might get faster instead of definitely getting faster by doing some CFOP thing better?
- They think that ZZ is worse because everyone is telling them that it's worse, especially if they're using EOLine.
Also, ZZ with EOCross is as much CFOP as CFOP with XCross is Petrus. Ie. It's not.