I do not understand how spoiler tags work on this newfangled forum system.
Now, for the combat.
My enjoyment of the combat really suffers from the fact that I had just completed Horizon: Zero Dawn with its constantly super fun and tense robot dinosaur battles. Going back to gunning down humanoids, robots, space dogs, and the occasional space dinosaur has left me feeling cold. There are a few very large enemies, but fighting them feels very similar to the end boss of ME2 with a few elements of the scripted dragon fights in DA:I thrown in. But those fights are few and far between; most enemies are on the scale of previous Mass Effect games; person-sized to small mech sized. ME:A, more than the original trilogy, really hurts from a lack of enemy variety. The vast majority of enemies in the game fall into the following groups on medium (or maybe hard) difficulty:
mobs with guns and no shields,
heavies with machine guns and shields,
tech enemies with tech powers, armor instead of health and shields;
Snipers with health and shields;
Stealth guys with invisibility, health and shields
monsters with armor and no shields, in small, medium, and large sizes with a few cosmetic differences and elite versions of the big ones with one-hit kills;
mechs with shields and armor;
floating robots with health and shields and beam weapons;
running robots that make drones that physically charge you through the air;
and robots that can set up their own cover.
I do not recall seeing a single biotic-wielding enemy. There are a few boss-class enemies not on this list, one of which kinda sorta uses a biotic-like power to float and teleport around, I guess. The gun-wielding mobs come in different flavors of aliens and humans, but they all function the same. Maybe some of them have grenades and others don't, but grenades do not matter due to your jetpack-dodge abilities. After dozens of hours, the variety gets very stale, and there have not even been new mixes of enemies. I mean, encounter escalation with the kett works like this: easy encounters have mobs and one or two guys with machine guns and maybe some small space dinosaur dogs. Slightly harder encounters add stealth guys and maybe a few more dinosaur dogs. hard encounters have tons of machine gun guys, mutliple stealth guys, dinosaur dogs and maybe a boss or elite monster that can one-shot you. Sometimes harder encounters just mean more waves of mobs and machine guys and stealth guys. That's it. It's even worse for the other alien races, although the robots at least are different enough from the milky way, kett, and angara encounters to be a welcome reprieve until you realize that you'll be dealing with ten robot-only encounters in a row.
Aside from enemy variety, ME:A further erodes the foundational shields/health/armor trifecta upon which ME combat has always been based. It's weird to shoot at a fucking turian with no shields and health, as if his armor is all that's keeping him alive. I also don't feel like the different guns matter all that much against the different protections; sniper rifles destroy any protection and automatic weapons chip them all away equally. Gone is the feeling that I need an SMG to dal with the hefty shields on a mech before switching to a shotty to take down the armor.
Some of the problems have long been in the ME games, such as the unending frustration that biotics have little to no effect on enemies with shields up or armor. I get why shields might protect one from biotics gameplay-wise and in the lore, but it's silly that armor protects you from being tossed about by singularity or pull.
The jet packs are good, and the improved mobility allows the level and world design to be more interesting. But sometimes it just seems to easy to keep jetpack-dodging away from every attack until your shields recharge.
There needs to be a better variety of enemies and, I believe, more large-scale enemies. I'd love to take down more gunships or a shuttle with my biotically-enhanced Ryder. The Initiative might be hard-pressed for combat vehicles, but the races of aliens that have been at constant war for decades ought to have more options than capital ships and piddling ground troops. Design the vehicles like HZD robot dinos to have weakpoints and attachements that, when removed, change the vehicles' behavior. The robots' mech-sized enemy has a hint of this in that you can destroy its gun turrets, but it's not nearly as interesting as any HZD enemy.
ME needs to rething the shields/health/armor trifecta. I'd propose having every enemy aside from bots or vehicles have health. Sheilds ought to block all damage to health and armor underneath, and ought to recharge and go back up after being brought down by gunfire. Biotics ought to only damage shields at high levels, but ought to degrade armor from the get-go and paralyze baddies in armor like they paralyze health-only guys. Armor should be very resistant to most tech attacks and gunfire aside from specialty ammo/weapons and should not regenerate on most standard enemies. Armor ought to protect against explosive weapons better, too. An enemy brought down to health-only ought change its behavior and act more defensively, too. And that's just scratching the surface.