Honestly, would anyone care about flight if it wasn't in Solasta? The majority of CRPGs don't bother with a flight system and nor did the many D&D implementations on PC I've had so much fun with.
I don't have a problem with them adding it, but I feel like they'll add something which will be a flight tag that just lets a character ignore most terrain and possibly get knocked down. People will have been instead expecting some hugely complex system and includes different levels of altitude and all other nuances and we'll just have the same exact threads about how the flight system is insufficient.
I feel like speculating about how players would use a system that doesn't exist and coming to the conclusion that people would somehow consider it insufficient is a futile exercise. I find the argument that a new combat option shouldn't be implemented because the community *might* react in a negative way to be tiring. Especially in regard to something that already exists in the source material.
Flight is supposed to be a double-edged sword. You gain extreme mobility, but also run the risk of being knocked down and taking immense fall damage. Spells capable of floating in mid-air suddenly become a lot more flexible. For instance, a flying flaming sphere can be used to chase down something else that's flying in the air, so maybe that enemy might think twice about trying to take to the air, knowing what kind of consequences would happen if they fail their concentration check to maintain flight. You wouldn't have to jump spam all over the place when traveling, and you have another answer to reach that distant ledge when exploring. Larian could add their own flair to it and let people start a fight by having an invisible flying party member straight up dropping barrels and other heavy items from the sky (or levitate said objects to achieve the same effect).
No one really loses anything by its implementation, even it turns out to be as half baked and largely limited to mobility purposes and stopping to attack in midair, which are the most practical applications of it anyway. But people would be happy with even that. They appreciate effort, not silence or excuses.
Sure, the Pathfinder games don't have flight either, but people clearly understand that it's because those are lower budget games. But people logically expected a lot more from BG3 in comparison, which places a much larger emphasis on having tactical combat. I think a lot of complaints about BG3 more or less stem from how badly expectations are being managed by Larian's PR, or by the community hyping everything up itself. If Flaming Sphere is rolling along on the ground because the engine can't support flight, then just straight up say so. People would throw lazy dev rhetoric around the first few weeks, but the majority will appreciate the honesty and the matter would be buried long before release.