The problem with cable internet is that the shared medium (coax segment) has relatively little upstream bandwidth, shared by 100's of users. FTTH has much more bandwidth and a smaller amount of homes sharing it. Typically there is a passive splitter / fiber distribution for 8 to 32 homes, at least an order of magnitude better than cable.
I switched to fiber a few years back. But at one point during covid, my cable modem upstream was getting less than a megabit (I was paying for 500/30.)
Correct, and in reality it's likely to be 100-1000x the capacity. Probably say 16 users on average on a PON segment, with XGS-PON having 10gigabit/sec symmetrical.
Compare that to docsis 3.1 - maybe 200mbit/sec between hundreds of users.
DOCSIS 4.0 is better but just basically brings the split much closer to the home, in which case you'd probably be better off finishing the job with FTTH instead of having thousands of expensive active DOCSIS terminals every few hundred metres.
Also, you can easily upgrade capacity on FTTH, just add a new OLT and you can run that side by side with the old one while you upgrade everyone's ONTs.