>I believe the general consensus of the informed is that Starship is going to take years longer than originally predicted.

Are you joking? That isn't even vaguely the "general consensus of the informed", at best it's "wishful thinking by old space types who are seeing the real time overturning of their gravy train". Frankly, at this point the major risk factors as far as getting to orbit are done. Raptor works and generates plenty of thrust. Starship can go up, complete a bellflop maneuver, and then land. And under harder conditions, they did an extremely aggressive fast landing to save fuel, much higher g's then they have to. The only critical component to save in SS/SH is the SH booster, which is where most of the expense is in terms of lots of Raptor engines. However, that's also the easiest part technically speaking, it just goes up and straight down again and SpaceX has proven capability to do that obviously. In fact fundamentally it's easier than F9. SH will have a minimum empty TWR (thrust/weight ratio) below 1, which means it's capable of hovering. F9 doesn't, so when they light up empty even a single engine on minimum throttle it'll still be heading right back up again. That's why they need the "hover slam" landing procedure, where they very carefully time things so that downward velocity and thrust counteract at exactly the landing height. Steel is easy to work with and more reliable.

People have this notion that "bigger is harder" but that's no in fact always true. And SpaceX has engineered every last bit about Starship as part of an overall self-reinforcing system. It's cheap to iterate. Mass manufacturing has been a core part of the plan from day 1. So they can be hardware rich, cheaply. Flight is also engineered to be cheap, from the materials in construction to the construction procedures themselves and right down to the fuel (RP-1 rocket grade kerosene is quite pricey, methane is not). And they can self-bootstrap thanks to Starlink. SpaceX can look at a true MVP: all they have to do to start iterating is launch SS/SH and recover SH, it's fine to have SS be fully expended while they figure things out and it will still be cheaper/kg (maybe even cheaper outright!) than F9. So they can be making money off it very fast, and then make more money once SS is landing too. They can do initial proof with their own payload, then riskier commercial payload, then full commercial, then manned, ironing out issues with actual real flight the entire way.

So what's revolutionary about Starship isn't merely the vehicle itself, but the entire system around the vehicle including the fact that "the vehicle" can pretty rapidly evolve and get tweaked.

There's a history of this. Case in point: Falcon Heavy. It ended up being delayed so long that improvements in the Merlin engine greatly reduced the payloads that Falcon Heavy was originally built for to the point there are a couple of launches a year at best.

No, you've got this completely backwards. The rapid iteration and increasing power of the F9 negated the initial economic proposition for Falcon Heavy, so they just didn't need to bother and put it on the backburner until F9 was fully baked. Then they didn't devote much more resources to FH because Starship will completely obsolete it anyway.