They’re pretty easy to counter in Rome 2, you just need to remember it’s necessary and not all-in on heavy infantry. Infantry skirmishers clap them right back to the steppes and there are good auxiliary cavalry options from the start available in Italy.
I definitely remember being frustrated when I first played it trying to chase them around with legionaries but the correct answer is don’t do that then.
Also because they were absurdly expensive for the civilizations that were using them. The loss of their chariots to Sea People invasions and the cost of replacing them is sometimes listed among the reasons for the Bronze Age collapse of the Hittites and the decline of Egypt despite their battlefield victories.