I think you have given yourself the answer.
As a new EV car manufacturer that is struggling to become cashflow positive, Tesla would never have the financial resources/cash flow to be able to fund research on FSD while trying to ramp up Model 3 production for customers around the world who are screaming like little spoilt brats for their shiny new cars...
While I am "dreaming" about FSD, Tesla is busy developing it, amassing data from Tesla's car fleet, with teams of people working on making FSD happen.
When I registered for my Model 3, I had no idea if it would be delivered within 2, 3 or 5 years - actually at the time, my son was leaning more towards the 5 year number than the 3 1/2 years that now seem likely. Along the way, Elon gave what were his best estimates - based on the information available to him at the time - as to how he expected production to ramp up. All the while, people complaining about panel gaps, poor paint jobs, rattling sounds, "exploding" batteries and a press that was only too happy to slap dramatic headlines on all of these issues...
Likewise, Tesla is trying to develop FSD - something no other auto manufacturer has fully mastered at this point in time and something most other manufacturers are attempting to solve by applying different technology to Tesla. So we know that many problems that Tesla encounters in developing FSD are being encountered for the first time, as it is treading new ground - Tesla is literally going, where no other car manufacturer has gone before...
Again, no one is putting a gun to your head to sign up for FSD. Anyone who does put money on the table and thinks that it will be developed according to a set time table is probably not that smart. Anyone who does not understand that Elon's "unfulfilled promises" are anything more than his best estimates - is probably not all that smart either. As to anyone who signs up for a class action due to FSD's "unfulfilled promise" on the other hand is any litigation lawyers dream come true.
All imho