Using plpgsql to remove all functions
Your code is executed in a single DO statement and hence in a single transaction. So if any of the statements cause an error, all statements will be rolled back.

If you want to avoid that, you can use subtransactions by using an EXCEPTION clause, for example:

BEGIN
    EXECUTE format('DROP SEQUENCE %I.%I',
                   myschema.schema_name),
                   myseq.sequence_name);
EXCEPTION
    WHEN dependent_objects_still_exist THEN
        RAISE WARNING 'could not drop object %.% because of dependencies',
                      myschema.schema_name,
                      myseq.sequence_name;
END;


Then the failed statement is rolled back, but processing continues.

Another thing you could consider is using

DROP ... CASCADE


which will remove dependent objects automatically.