Floodgate may be worst than vanilla Trap Hole depending of the monster, because it block a monster zone AND prevent you from special summoning it again from the graveyard. But a 3 Floodgate + 3 Trap Hole deck is 🔥.
Doubt any good deck-builder will use six trap holes. They're useless against monsters that are already summoned: not as good if you go second, and horrible topdecks.
Since the trap hole you mentioned doesn't work on special summons, I think it will hardly be as dangerous as this one. Bottomless trap hole, on the other hand, may be the real threat.
We're not ready yet for bottomless until at least synchro's been release. That 🔥 just destroy any monster that been summon(s) with 1500 att or more, no cost and banish that monster(s). Just imagine the p2p player with 3 copy of this card in all of their deck
Of course we are not, I was just giving an example of a card that is actually stronger than floodgate trap hole, since we were mentioning other types of trap hole. Hopefully we won't see bottomless trap hole any time soon. Rather than synchro, that card might be acceptable if they give the possibility to make viable decks that rely on banished monsters.