The lake is a perfectly good idea. It provides a venue for a night spectacular AND still contributes to placemaking and the broader feel of the park. Unlike say Fantasmic in DHS that is empty all day long.
It also critically stops making the park feel like it is merely a bunch of boxes dropped into a field or paved parking lot.
Yes, Avatar is pretty well established as not a risky move at this point. I get the hesitancy of the DAK land (which was a success) and the hesitancy around the long delayed sequel (which was basically France's biggest movie of all time corrected for the exchange rate). Iger is a long champion of Avatar/Pandora.
What do they need to wait for now exactly? By now it's a safe move. A 15 year old franchise that was just last year tested with the French/European audiences again, to resounding success.
I concur with your outlook. It reminds me of what Disney was doing at Disney's California Adventure early on. As DCA struggled, Disney responded by green lighting a series of hastily built additions. Most prominently, a Bugs Land and Tower of Terror came out of this fraught time. Both those attractions were successful, but they failed to fundamentally transform the park's prospects. Why? Because the park was structurally flawed. The placemaking and circulation were poor. Good rides and IP connections were not enough to change the problems faced by DCA. What was needed was a more fundamental transformation. One that did involve additional rides, but not exclusively rides.
It's honestly the opposite problem faced by DAK upon opening, which had fantastic placemaking but a dismal portfolio of rides. In that case, building rides really was what was needed.
It is unfortunate that a significant amount of WDS's budget is going to a lake, a promenade, and fixing other problems that shouldn't have existed in the first place. But it is absolutely necessary. Even beloved expansions to WDS like the Nemo Coaster, the Rat ride, and Tower of Terror were not enough to end the park's pain. A lake isn't as a flashy as a new E-Ticket, but by creating it they are fixing structural problems facing the park. This lake will address the woeful circulation of the park, add greenery and water, and make the park beautiful. And once it makes it through this, additional expansions will be much easier to implement. The lake opens up all sorts of opportunities for new lands.
If I was to critique a few elements of the project, it would probably be the order of operations, the speed of implementation, and choice of IP. Reskinning Rockin' Rollercoaster seems like it should have been down the list of priorities. One could easily argue back that it was low-hanging fruit and a way to have the park gain momentum rapidly. Perhaps it was a way to get something marketable while the more substantive expansion came later. Still, it strikes me as odd that they would devote resources to overhaul something that was successful over spending on something new. Of course, in the long run it will all be the same.
The speed of implementation really seems to be making people frustrated with this project. Myself included. And of course they have a good explanation with COVID. It's hard to argue with that. Hey, we can still be frustrated even if it's not totally rational!
And then the choice of IP. This one seems the least defensible. The Pandora land seemed like a no brainer even in 2018. I was very surprised 5 years ago when they announced Star Wars over Pandora. By then Pandora had opened to great success at Disney's Animal Kingdom. Between France's affinity for Avatar and the huge success of Flight of Passage, it was really confusing. I've seen people point out that Pandora could easily have been brought indoors to create a constant bioluminescent environment. You could have essentially moved the floating mountains and Flight of Passage show building facade to be the facade for the indoor land. That way you still have good views on the lake. Then you go through a cave into the bioluminescent world. Shops, restaurants, placemaking, and queues all could have been in a temperature controlled environment safe from Parisian rain and snow.
But they chose Star Wars... Anyone who doubts how popular Avatar is in France has to look at the box office gross. It's insane. That one will never make sense to me. Sooner they can move forward with a Pandora land the better. An advantage is that spending on the Walt Disney Studios Park Pandora has the potential to benefit DAK's Pandora. Updates to ride technology, new food, placemaking, and effects can be shared. I hope they move forward with it!