I guess if you're that opposed to the mechanic, then I guess this particular game is not your style, and will never appeal to you unless an option to turn off unlimited reinforcements is added.

FTL had similar reactions - personally I like it when a game throws insane stuff at me, then laughs as I try to survive against the odds, but some people just couldn't stand it.

With endless reinforcements, both XCOM2 with the Long War 2 mod and this game achieve a sense of being a small team in enemy territory, where once discovered (or straight away, in some missions), you need to do what you need to do, as quickly as possible because hell is about to be unleashed upon you. It brings to mind those spy action movies where their home/safehouse/base is raided, or where they do a raid with meticulous planning only for the enemy to discover them and all hell breaks loose, and suddenly you're no longer the assassin/thief in the silent shadows - you may be tough, but the enemy is relentless and won't stop, so you need to "GET TO DA CHOPPA!" (or van or whatever) before a horde of enemies take you out.

It's a shame you no longer have the game though, because once you get used to how the combat works, it becomes much, much easier. I'm now at the point where I'd welcome a level above Hard, to crank it up a notch - but that can wait since I still haven't completed the game yet, and if some mechanics are changed this may not be necessary.

The one thing it definitely shares with the XCOM games: killing the enemy as fast as possible once combat starts is crucial. The way to do that here differs: here if someone has high awareness, you need to reduce that first before taking them out, and to do this in one turn always requires two agents: one to fire a full auto, which apart from damage will instantly remove their awareness; then another to finish the job, which may require only a single shot, maybe a burst, or maybe a pistol head shot (in which case you need someone with a pistol to be close enough and with enough awareness for the headshot).

The way it differs from XCOM is that in addition to always ensuring all of your agents are behind heavy cover if at all possible, you also should ensure that their awareness is as high as possible at all times. I've had one agent dodge at least two attacks, then get hit with two more - and those didn't do much damage because he was in high cover.

Then factor in that you can always do max damage at point-blank range, and firing pistols doesn't end your turn (and I believe also costs no movement points at all?). This can be exploited pretty easily by the player at the moment - the AI currently either doesn't realise that point-blank range is a thing, or they prioritise cover over kills. Luckily the AI doesn't HAVE to be exploited in order to win, even on hard, because to me that kind of thing feels overly cheesy.

Oh and finally: the mods to the side-step thing (mentioned in the OP) makes the combat feel a lot better already.