Think of it this way. The normal "combo" in the game is to play some creatures, then use removal to destroy the the other creatures and deal damage with yours. Eventually, one of your creatures deals enough damage to defeat the opponent. That doesn't mean that creature is overpowered or anything, just that you played a game until you set up the state of the board to win.
The real combos work in such a way that the rest of your pieces aren't dealing damage but are instead controlling the board so that you get enough time to win with a couple of powerful synergistic pieces. You expect these types of combos to defeat you in a single move, or two at the most, because they are hard to set up and possible to disrupt. This is most certainly the case of flytrap and heartichoke. There are various strategies that defeat it consistently, including Valk otk. Also super aggressive decks like aggro dancing can defeat it before it can go off. Any deck with cheap environments can easily disrupt it too.
To me the proof that this particular combo isn't overpowered is that you don't see many people playing it at Taco league, unlike something like Valk otk which is much more popular due to it being far more consistent.