If it's not your cup of tea, that's fine. I remember when the house building DLC came out for Skyrim... and I didn't care. It wasn't what I was looking for, so I didn't get it.
What I object to (or more specifically, find kinda hilarious), are the diatribes about how it's an affront to the series "realism" or "believability', and how "no one asked for this", and so on.
There's a reason the sales of this series have eclipsed the Motorsport series - it's aimed at a broader cross-section of players, than "car guys' who just want more straight-laced motorsport content. Outside of the hardcore racing game community, the reaction to the trailer for this expansion was almost universally delight at how silly and fun it looked, and people saying things like "huh, I'm actually interested in a Forza game for the first time ever".
If you just want race cars on race tracks, there's an entire other branch of Forza tailored to you.