PgAdmin4 unusable when database has lots of schemas

I have a production database with 60K database schemas. PgAdmin4 is unusable, I cannot even open "Query Tool" window. I suppose that PgAdmin tries to load database metadata, so that's the reason why it's so slow. Is that true and can it be disabled? Can I do anything to speed it up? I tried to use other DB clients like DBeaver or TablePlus and I have the same problem.