Even if luxes were nerfed in this fashion, I don't think it would make sense to prioritize building an entertainment complex to avoid a -5% unhappiness penalty on yields in lieu of building the districts that will generate those yields. Build the campus first, and later maybe patch with an EC.I think +3 Amenities per luxury might improve the game. You'd still be able to be expansionist, but you'd be required to prioritise entertainment complexes, which are pretty underwhelming atm unless you're playing with sparse resources.
So in your example above, the need for EC would slow down your construction of campuses.
It would still be nowhere near as restrictive as happiness in Civ 5 since nothing stops you from successfully expanding, but there should be better opportunity costs.
Edit: Another approach is to increase the yield bonus in Ecstatic cities.
And in nerfing luxuries, the map is even further nerfed. If a player hunts down luxuries to get amenities, the that's some kind of strategic approach to expansion. If the expansion meta is all about districts, not the map, might as well spam. What is needed is to both increase the impact of happy/unhappy, and have the unhappiness be impacted an expansion factor, like distance from the capital or number of cities relative to some development metric (which Civ VI isn't big on providing).
But of course, we should know from the very comments of Dennis Shirk and the rest of the dev team that this kind of talk amounts to swimming against the current. Civ VI is not about careful planning and measured moves. It is chiefly about the "whee" factor of constant growth and unchecked snowballing. The loyalty system is a standout, and while not's heavily influenced by amenities it's sufficiently influenced by them that when I go colonizing, I do look to settle or capture based on access to new luxes.