We sampled some high end balsamic vinegar when we visited Italy in 2018. It was bottled and aged by the Verrazano family - they have a bridge named after them.
They age their balsamic in casks for like 30 years or something What comes out is kind of a savory syrup. It didn’t taste like vinegar at all - no astringency.
I’m not sure what I’d ever use it for.