When people say string theory was discovered, it is not as if someone saw a particle up close with string properties.
It is a theory that is used / imagined to try to explain the contradiction and as yet there is no proof.
This reminds me of reading old papers where John Dalton proposed the atom as a solid sphere.
Do we have proof that black holes radiate?
Is it convenient to assume a black hole is a hologram and we can’t see whats in it so we can say anything we like about what might be in it. A bit like Schrodingers paradox?

Do we need a single combined theory to describe everything we see?
Some would say yes, there must be a way to write down a “formula” for how the universe works from the smallest particle and force to the largest mass and galaxy etc.
Maybe we don’t know enough yet to be able to combine it all together.
There may be another “quantum leap” to release a new subject area to expand our knowledge base.