For me, the issue isn’t restricting flight in combat. As you observe, the DM has plenty of tools for dealing with that. For me, the problem with races that grant flying at level 1 is that it makes it so you can’t use flight as a gating tool. Normally, you can count on players not being able to bypass certain obstacles until certain levels, and use those obstacles to restrict areas in a dungeon-like or hexploration environment. Allowing flying races without a restriction like having to end their movement on the ground or fall means you can no longer count on a category of obstacles to work as effective gates.
Well, lets look at it this way: there are 2 primary flying @ level 1 races in 5E, variant tieflings and aaracoka (or however you spell that). They are both obscure races and do not appeal to a lot of players in the same way dwarves, elves, humans, half-elves, halflings or even half-orcs do.
Even at a 20 str, a flying creature is
at best only going to be able to carry one other medium or smaller creature and only then if they are within the usual weight ranges and that's also when said flying creature is almost totally unencumbered.
Obstacles that require flight to access will still be obstacles. But lets face it, how severe are obstacles that require flight? A tall cliff? A tower with a door up top? A large chasm? At best, the flying character is going to be a scout, and
maybe if they see things are all clear, a taxi for the rest of the party. And that's assuming that they maxed out strength. If they didn't, the party is still stuck with needing flight to access, and only one player is able to get across without it. This one player is essentially splitting themselves off from the party and making themselves a big obvious flying target for any enemy that may be hiding out in the place that requires flight to access. It means they will be isolated from the party if they need healing or other support, it could get them trapped.
The tradeoff for being able to jump over small obstacles at low levels is the increased risk of isolation on the other side. A giant bird-man is not a tiny spirte (which the wizard or any human who takes Magic Initiate feat for Find Familiar has), which is arguably much better for scouting than BirdMan.
Besides that, as pointed out in the post you quoted, the obstacle simply becomes the wind instead of the distance needed to cross with flight. Wind can be devastating even to non-flyers in canyons, cliffsides and exposed areas.
As a person who has run flying characters a lot, I'll break down some of my uses for it:
Flying up tall buildings/cliffs.
Scouting from really high up.
Flying over large canyons.
Generally being disgruntled when someone in the party asks for a lift.
It doesn't do me any good in dungeons, heights and holes are still a problem for me there. It doesn't do me any good in a building of any sort. A tight canopy of trees makes my life difficult as I can't fly up, and if I can get out, I can't shoot back down.
So, much like the dreaded Sniper feat, flying is really only a problem on the theoretical level in unlimited open spaces. As long as spaces are constrained by believable obstructions, flying is about as useful as having a spirte familiar.