You posted in FTL but seem to be talking about Into The Breach.
Yes, it's that hard. Especially for seasoned gamers. The goals in the game (from flavor text) match what you as a gamer expect, but the actual winning strategy is quite different.
Your mechs heal fully for free after every battle. Therefore, mech health is a very low priority until the last shot that will kill them.
"Optional" objectives *ARE* the objectives. Almost anything - except *possibly* a pilot's life - is less important than those optional objectives.
People dying in buildings is bad, but of most of the bad things in the game it's the least bad. I'll take a hit to a mech instead of a building if the mech will survive, but if that building damage means I keep an objective or mech from being destroyed, sorry Billy you're dying today.
In addition to that, there are a few things that are not obvious on first blush.
Pushing is SUPER powerful, as most vek die instantly in water.
Knowing how many hp a vek has by sight, and how much damage it will do, is important on the main map screen when deciding what island to go to. This is more important later.
Turn order is critical. Click that icon on the top of the screen that shows it, and try to get the vek that move first to kill the ones that move later.
There are a million other little things, but those should get you through Archive and RST, and possibly the final battle even
