What I really don't like about TCM, is the disparity between cars in each class. Some cars are so meta and others are completely useless. And you can't compensate this with tuning. Upgrades aren't car specific anyway, so they don't count.
For instance, while I was grinding parts for Rally Raid by doing Hummer Xpress, I was testing all my available cars (about a dozen) with default tune. The best car (currently available to me) was the Nissan Skyline Rally Raid, great handling offroad and on tarmac, very fast. The worst one by far the Mustang Rally Raid.