Well this is probably a hornet's nest all on it's own, and theres no need to derail the entire thread for something like this but I guess I'll bit. Twin does have negatives to the format, it did when it was legal, not everyone was sad to see Twin go when it was banned, there were plenty of people who enjoyed the Twinless format (at least until Eldrazi winter came).
For me personally, I had experience playing against a local veteran who ran RUG Twin, the issues I had playing against the deck were that it had:
Good Counterspells (Cryptics, Leaks)
Tempo Plays (Remands, Pestermites, Exarchs)
Agro Potential (Goyf into Bolt Snap Bolt)
Legitimate Control Potential (Cryptics + Snaps)
And of course, game ending threats (Twin or Blood Moon)
Really the deck had A LOT going for it, it really enjoyed an ease of play that other decks simply didn't. Back then I played various meta and non meta decks against it, everything from Affinity to BW Tokens to GW Hatebears (remember voice of resurgence lol), and the thing I hated most personally was simply knowing that I wasn't allowed to play magic, I couldn't tap out to play my relevant cards and the Twin player didn't have to since they had access to Goyf, which back then was a top tier threat. Even doing typically things like Pathing a Goyf felt awful since I knew it would simply speed up their combo.
Mind you some things have fundamentally changed since that time, for one thing, Gitaxian Probe is no longer here, and that was a very relevant card that Twin could and would lean on. Removal has gotten marginally better, push and trophy are welcome additions though they aren't always better than Path, but at least I assume we wouldn't have to play garbage like Slaughter Pact like we did back then which felt awful as well.
Honestly I'm not sure how I really feel about Twin if it were to be brought back into the format, my gut reaction is simply that we would be making another giant paint bubble (spongebob meme) which wouldn't fundamentally help things, and I don't know what the appetite is for the playerbase in terms of adding more A + B combos at this point. At least with Pod, it required 3 creatures, all of which were soft to bolt to combo someone.