Are Generalist attackers the biggest winners?

I know there was speculation that generalists may lose their importance with STAB being less important and SE damage being more important. Raid battles aside, I think a set team of 6 is the only way to go...

Between the battling I did last night, and just now at the park with my kids, I noticed that gyms so are easy to take down with the decaying cp. Match-ups are almost irrelevant after the second time around, as your pokemon have such a massive advantage (your 2500-3000 cp pokemon vs their 1500 cp pokemon.) I wasn't even switching out my Rhydon vs Vaporeon or my Venusaur against Flareon, as I could take them out so quick.

My conclusion is that to take down a gym as fast as possible, you are only looking for the highest dps pokemon to blow through the weak team.