Gishiki are FAR from "shit" and are missing some cards, including 2 Ritual monsters & 2 searching monsters that also can be used as the entire ritual summoning requirement, & also have stricter Level summoning requirements.
If they had these cards, Gishiki would probably be considered 'OP' but idc, they are a fun Archetype. Try them out in the real game~
Aliens are a completely different story as they were never given enough power to ever really be a threat to anyone.
And in this modern age, Aliens still pose no threat to any real deck but does have some powerful Reptile monsters. That's about it.
Yeah Aliens were never really good. But their key card was their synchro monster that could return face-up s/t's to hand (allowing constant reuse of some choice continuous spells), dumping A-Counters essentially for free, and popping cards at a really low cost.