
Fire/Water/Grass Type Cores
People actually buy this >_<
I get a similar impression when I read statements hating on the use of Fire, Water and Grass type pokemon together. Like an old women designing a hoody, it shows a poor understanding of the real situation. People don’t always use Fire, Water and Grass type pokemon as a 'core' and suggesting that it’s a bad thing to use all three together is obviously stupid.
1. Firstly it’s not always used as a ‘core’
Heatran is on 50% of teams and Infernape is on 25% of teams, which means is that Fire types are incredibly common. Water types are probably the most common type in the tier (bar steel), every single competitive team seems to have a water type these days. My point is that that Fire and Water types are extremely common. So whenever you use a grass type, it's extremely likely that you'll have the Fire, Water, Grass combo.
2. FWG isn't a bad thingSometimes FWG is used as a core and it can be really effective. I don’t understand that mentality that “FWG doesn’t gain anything”. Here are a couple of examples of Fire, Water and Grass type pokemon with good synergy:



Physical Infernape and Sub Punch Breloom are an excellent wall breaking combination battering their way through walls like Rest Talk Gyarados. They can happily switch in each other checks like Vaporoen and Celebi respectively. Breloom’s spore is a key feature of this core, luring out and crippling things that check this trio. Dragon Dance Gyarados is the perfect sweeper to take advantage of the holes Infernape and Breloom create.



A different style of core. Roserade and Heatran having excellent defensive synergy allowing them to set up entry hazards easily (spikes + stealth rocks in this example). Starmie completes the typing synergy and provides rapid spin support, allowing complete entry hazard domination and makes switching between the three pokemon a lot easier.
I understand that there is a problem when some people slap on three random Fire, Water and Grass type pokemon. Needless to say, this is bad teambuilding. But that doesn't make using all three types together a bad thing.
Tl;dr
FWG isn’t always used as a ‘core’ and when it is, it can be effective.