There are few hard constraints, and almost no criticism is in that direction. Sure, I'd wish to see Parpaillon in the Tour, but I don't blame ASO for not moving heaven and earth to make it raceable. I'd wish to see a Tour of more than 4000 km and with no rest days, but I don't cry about that every year.
There are trade-offs, design philosophy, habits etc.
Those are not constants. The Tour has changed a lot, and has over time offered a wide variety of routes. When you pay attention to the routes of the Tour, you can infer intentions and what in a given time is considered as viable options (or just plainly listen to what they say). Several combinations of climbs or novel ascents have been talked about or proposed, and then later featured. Because we mostly consider viable options. Like Iseran-Tignes, Bonette-Lombarde-Sant'Anna di Vinadio and Aubisque-Spandelles.
The previous finishes in Rouen have been boring flat stages. Next year has a hilly finale. Because they actively chose that. The Tour hasn't had a long ITT since 2014 (longest was in 2022 at 40.7 km). Because they have actively chosen that.