You don't seem to understand that just like in F1, NASCAR teams are constantly in development, and although it's not a "new car" each year like F1, the cars are different enough year over year to effectively be "new". Like, a Gibbs car in 2021 is going to have a lot of different tricks and findings under the skin that you can't see on TV compared to a 2018, 2019, 2020 car, as engineers find small gains in different areas of the car and NASCAR closes loopholes. Look at SHR losing their wheel well advantage this year causing them to lose downforce. Their 2021 car is a "new" car because of that.
In regards to the bolded text above, I recommend an idea for you called "letting things go".