I don't think there is anything wrong with B2B SaaS. I think that's a red herring.
From my experience, the conformist attitude we see on display these days comes from FANG salarymen ("salarypeople", the reference to the Japanese cultural concept of "salarymen" is instructive). They have treated tech as nothing more than a fancy bourgeois "career path" -- like high finance in the 80s or big law in the 90s. An inoffensive way to make their parents happy and raise families with a good standard of living. Nothing inherently wrong with this, but it does mean the rebellious streak in the culture begins to fade.
As I remember it, the utopian feeling of tech communities of the early tech culture stemmed from cyberpunks homesteading the noosphere (a la Linus) or engineers-turned-accidental-entrepreneurs (a la Woz). A large part of it was the sheer thrill -- the fun -- of creation. It's not B2B SaaS that drained the fun out, plenty of fun B2B products were built in the post-Linus, post-Woz area. What drained the fun out, instead, is the corporatization of the entire industry via Big Tech.
We all used to complain about IBM/Microsoft in the 90s and 00s, rebelling against their industry dominance via open source (e.g. Linux) or engineering+design (e.g. Apple). Now the same sorts of people work for any number of IBM/Microsoft-sized corporations, exerting IBM/Microsoft-style proprietary control over individual lives, in comfortable salaried roles in the 2020s.
I'm not sure what to make of it, myself. On the one hand, "tech won". Heck, even Linux and Apple won, beyond my wildest imagination in the 90s and 00s. On the other hand, so did conformism and stagnation.
(There were other similar victories, I am just using Linux and Apple as easy illustrative examples from the last couple decades.)
Reminds me of this quote by jwz from way back in 1999. He was writing about Netscape but you could say the same thing about the whole tech industry today:
The company stopped innovating. The company got big, and big companies just aren't creative. There exist counterexamples to this, but in general, great things are accomplished by small groups of people who are driven, who have unity of purpose. The more people involved, the slower and stupider their union is.
And there's another factor involved, which is that you can divide our industry into two kinds of people: those who want to go work for a company to make it successful, and those who want to go work for a successful company. Netscape's early success and rapid growth caused us to stop getting the former and start getting the latter.