Racing against the AI is far worse. Racing against humans will often get you close and fun battles. And, depending on your own behavior, it will be clean and respectful racing far more often than not. If it really was that bad in every race it would be a ghost town. The fact that it's not shows that these are the exceptions.
Yet that doesn't excuse getting penalized for unavoidable situations or getting unfair penalties from other's behavior. Especially not since a few of those incidents can drop your safety rating a lot, which makes matchmaking worse and you'll be denied those fun and close battles until you restore your SR.
However despite the problems it's still the best way to get into a quick competitive and often respectful race.
It's now an art to scrub the penalties right before the finish line. Move over, brake just in time and cruise over the line as the count reaches zero. You can burn off over twice the gap difference to who is behind you. And why wouldn't you. If you have 1.1 sec penalty and the next person is 1.5 sec behind you. Why give up the position by it getting rounded up to 2 sec.
I checked some of my replays of Monza, burned off a 3 sec penalty right before the line and the car behind me only gained 1.3 sec on me. Another one, 4.2 sec penalty in 1.7 sec. And another one 1.8 sec gone in 0.7 sec.
I was only 1.4 sec ahead. Got the penalty from someone bumping me wide in Ascari so I didn't feel like giving up the win.
I once made the mistake of doing that one lap too soon and was quite surprised the race kept going while I was crawling down the straight
Did not keep the lead lol.