Year to year it is hard to say, different courses and different temperatures and different tactics. Personally, as someone that has been an avid cycling fan since about 2000, I think it's pretty clear drugs are involved, just at a much harder to detect level. All one needs to see is Pogacar's TT to end the 2020 TdF.
I've said it so many times, but there is a documented history of doping in the TdF since the very first in 1903. Every single race has doping issues. That's fine too. I think anything you can do without mechanical assistance is fine.
If you have ridden your bike for a single century, you can get a feel for how absolutely brutally tough the TdF might be, and you'll realize it isn't possible to do at 26 miles an hour for 3 weeks without help.