Online circuit racing open lobbies was pretty much dead for months, especially if you didn't want to use RS tires. Dead, as in very, very few rooms and sometimes none. I've gone through entire pages of lobbies in the last few months and found no PP based circuit racing. It was all drags, drifting and run anything rooms. Anyone who says their circuit racing experience was ruined because of hybrids is full of crap because no one was doing it. And the number of rooms was way down. There were nights with less than 100 lobbies open. After hybriding, 250-300 was common.
The PP system was well intact with hybrids, outside of the crazy powered cars that break the PP system which are easy to spot and combat. I tried and tried and tried and so did a little network of us, to find combinations of grip, engine and chassis swaps that could make cars faster than those that were already the fastest and we couldn't do it. Made a lot of great cars, make many that were competitive in PP races that weren't in the picture before, but nothing faster than an LFA or NSX or an Elise. Those cars are already near perfection in terms of their combinations of grip and power.
In reality, nearly everything about hybrids was positive. The only downside were the cars that broke they system with massive amounts of hp and those were simple to spot and to eliminate, in other words a non-issue in lobbies with hosts paying attention.