We’re at the better horses stage of the cycle. What’s the next car?
They know they are blind to potentially better products, but they no longer have the time to gather the experience and confidence in the new products.
You can still doubt that quantum computers are physically realizable. Perhaps the number of qubits needed for error correction will turn out to increase fundamentally faster than the number of useful qubits, or perhaps there is some other fundamental limit that we will hit.
But the maths is clear: if it is at all possible to create a quantum computer, it will be faster for certain specific problems than a classical computer (in particular, it will be faster than a classical computer at simulating quantum phenomena).
Still, it is strongly suspected that BQP != P. This was especially reinforced by the MIP* = RE result, as far as I understand from Scott Aaronson [0].
[0] https://www.scottaaronson.com/blog/?p=4512#comment-1829033
https://gilkalai.wordpress.com/2020/12/29/the-argument-again...