Beck, without the right DLC weapon, has no real ability to fire up or down. The enemies that appear above or below are very often ideally posed to be difficult to reach without taking a shot or risking spikes. While these are staples of series that may have come before, it never really feels valuable.
Beck very much has the ability to hit enemies that are either below or above him, one such abilities comes with Battalion's special weapon. The exploding grenade can be used to great effect to hit enemies that fly out of normal reach, Countershade's sniper does a similar job, as does Aviator's weapon for enemies above you.
Also, a lot of airborne enemies can be taken out by walking away and luring them down to your level, or climbing on something to get to their level. In my experience I only found one enemy that felt unfairly placed, that is, until I got good, dashed underneath it, climbed up on a ledge and shot its ass out of the sky.
The game, by design, encourages the player to play fast and loose. Count the exact number of shots it takes to destabilize an enemy, and dash into them immediately. Any less haste, and the Xel recovered bleeds between 10-30% within a second or two. This has a negative impact on the score, keeps Beck in the thick of fights, and means that cautious, patient play will result in getting to the boss fights with 3 lives but no ability to heal.
Actually, the Health Tanks fill up equally no matter how high your percentage of absorption, as can be seen here.
If a player hits an enemy in their stun frames, or just barely misses with a careful string of shots, they'll dash directly into damage. If hit during the dash animation, players have longer stun and are knocked back further. This means that aerial enemies who fail to destabilize for whatever reason will almost assuredly knock Beck into a trap, spikes, or bottomless pits if the player manages to fumble their shots perfectly. The stages are designed for this, with enemies and hazards placed exactly where one would expect to catch a bad case of death. These will almost assuredly result in at least one death.
That reason is the player being bad at the game, same way as it's the player's fault when he mistimes the parry shot in Bloodborne and gets his straight in the face, it is the player's fault for dashing into an enemy that isn't destabalised yet. And to be fair, some spots in certain stages are designed like this, yes, however, it isn't as common a thing as this sentence would lead people to believe as most of these spots can be circumvented by taking your time to analyse the situation and act rationally, rather than rushing in guns and dash blazing. If you don't know what the stage will look like 5 seconds from now, maybe you shouldn't be dashing in head first at top speed.
It is tempting to continuously press down the right d-pad button and keep smashing the dash button, but it's a fool's way of playing if you don't know the stage or its enemy positions. Deaths brought on by such reckless behaviour isn't on the game, but the player. For example, I wouldn't run through Dark Souls with the sprint button activated at all times, that is a surefire way for me to get jumped by an enemy or run into a trap and I wouldn't blame the game for it.
It seems that a lot of people went into this game with the mindset of; "well, I have played some Mega Man in the past, I can just breeze through here", only to find out that they don't know the layout of levels, position or abilities of enemies, or of Beck and then find themselves dying a lot because they behave recklessly. People forget that even though they have played a lot of games in the past, every new game has the ability to throw new challenges at them and can ask the player to learn a new skillset in order to cope with these challenges.
That isn't to say that there aren't spots in the game that made me scratch my head, absolutely, but I only found three of these spots and they weren't difficult enough to taint my overall experience of the game and were easily traverse-able the second time I came around to them.