Yes 63 Identifier limit is a real pain, especially for constraint names, where a long name can convey a lot of valuable info.
NOT IN FKs ie opposite of current FK’s for IS IN, would be useful for XOR constraints I would guess they could be implemented quite easily using existing FK infrastructure.
Not the worst thing in the world. I have trouble reading code with very long identifiers. Conventionally, a line of code should not exceed 80 characters or so. That's pretty hard if identifers are 60+ characters by themselves. If your project has standard abbreviations for things, "63 characters ought to be enough for anybody"
I had a project last year where DB names were autogenerated per tenant, with the tenant ID being a UUID, so you're left with 63-36=27 characters. Starts to feel narrow.
(Putting tenant_id as a column was not an option because for each tenant, a third-party software was started that wanted to have its own DB.)
