Same here, and I doubt we’re in the minority (anecdotally speaking, everyone in my raid group in WoW days hated gimmicky fights). So it’s a double edged sword for the designers imo - on one hand the mechanics of fights have to support flight mechanics to make the feature justified - on the other hand they can’t exactly make them mandatory because not everyone would like them.
You already mentioned above that it will be possible to make a flight build - which is a good start and essentially turns the mechanic into a different class, one that will likely be focused around cooldown/cdr, based on what I’ve read about flight mechanics in Anthem so far.
The other solution is to make the flight mandatory during specific phases of the fights - either to quickly change location, for example moving to a target 300m away that just spawned and has to be bursted down, or the arena gets flooded with dangerous substance so you have to go in air to avoid it, etc. There are lots of possibilities.
For me the ideal scenario would be to introduce some weak points to (larger) enemies that are hard to reach by standard ranged weapons (assuming the game has some kind of falloff system) but can be exploited easily by a flying mech. This would allow the group to bring one player who focuses on flying, for those who really want to, without forcing others to spec the same way.