Genesect helps bug, and is far from broken in that mono, considering most fire types stop it in it's tracks, and like previously said, if psychic people worry, do what every other monotype team does and STEP OUTSIDE OF YOUR GENERIC COMFORT ZONE AND PUT SOMETHING ON YOUR TEAM THAT ISNT SLOWBRO, MEW, METAGROSS, MEDICHAM, MELOETTA and try something new.
The problem I have as a psychic user (who only has the bro and mew of those you mentioned btw) with genesect is not stepping out of my comfort zone to stop it, its the in game strategy, or should i say, lack thereof, thats needed to kill it. Even the best psychic walls cant switch into a u-turn and live to survive the next poke:
vs. Slowbro, arguable the most viable and popular physical psychic wall
248 Atk Genesect Explosion vs. 252 HP / 252+ Def Slowbro: 173-204 (43.9 - 51.7%)
+1 248 Atk Genesect U-turn vs. 252 HP / 252+ Def Slowbro: 218-260 (55.3 - 65.9%)
vs. Cressalia, a more fortifying physical wall, but without regenerator to switch in and out and to take multiple u-turns
248 Atk Genesect U-turn vs. 252 HP / 252+ Def Cresselia: 138-164 (31 - 36.9%)
+1 248 Atk Genesect U-turn vs. 252 HP / 252+ Def Cresselia: 206-246 (46.3 - 55.4%)
vs. Metagross, perhaps could be viable as a physical wall? but doesnt have any recovery besides rest
248 Atk Genesect U-turn vs. 252 HP / 252+ Def Metagross: 66-78 (18.1 - 21.4%)
+1 248 Atk Genesect U-turn vs. 252 HP / 252+ Def Metagross: 97-115 (26.6 - 31.5%)
vs. Mew, maybe can survive a hit after a non-boosted u-turn before roosting, but not if boosted
248 Atk Genesect U-turn vs. 252 HP / 252+ Def Mew: 156-186 (38.6 - 46%)
+1 248 Atk Genesect U-turn vs. 252 HP / 252+ Def Mew: 234-276 (57.9 - 68.3%)
Or maybe you want to leave your poke who just got a kill in to take on genesect:
vs. Mega Medicham
248 Atk Genesect U-turn vs. 0 HP / 4 Def Mega Medicham: 124-147 (47.5 - 56.3%)
+1 248 Atk Genesect U-turn vs. 0 HP / 4 Def Mega Medicham: 186-219 (71.2 - 83.9%)
vs. Mega Gardevoir
+1 248 Atk Genesect U-turn vs. 0 HP / 0 Def Mega Gardevoir: 229-271 (82.6 - 97.8%) (would always be att boost unless physically defensive)
vs. Victini (non-scarfed, or scarfed after using V-create which would let Genesect attack first)
248 Atk Genesect U-turn vs. 0 HP / 0 Def Victini: 109-129 (31.9 - 37.8%)
+1 248 Atk Genesect U-turn vs. 0 HP / 0 Def Victini: 162-192 (47.5 - 56.3%)
vs. Espeon (because why not calc a poke that's super-effective against it?)
+1 248 Atk Genesect U-turn vs. 252 HP / 4 Def Espeon: 486-572 (145.5 - 171.2%) (would always be att boost unless physically defensive)
The amount of fast, very common, hard hitting bug pokes (mega-pinsir, scarf-heracross, volcarona) make it near impossible to take a u-turn hit and survive the next move.
AND THIS IS ONLY IF THE GUY USES SCARF U-TURN. God forbid its special and you switch in your physical wall slowbro to actually see a tbolt.
Its too powerful, its movepool is too diverse, and u-turn lets it run wild on psychic (but also dark and grass just as good). If you want to beat Genesect with any one of those three types, you either need your opponent to be an idiot and let it die when you switch in scarftini, or somehow kill the other 5 pokes and have atleast 2 pokes who can survive a u-turn and do enough damage to kill at the end. NO AMOUNT OF PREDICTING CAN ESCAPE GENESECT, THATS THE PROBLEM WITH IT IN MONOTYPE. IT IS THE ULTIMATE PSYCHIC/DARK/GRASS REVENGE KILLER, and I'm sure moves like flamethrower, ice beam, thunderbolt, iron head, and extremespeed make it a pain in the ass for every other type as well.