As someone who S-ranked all the campaign from the get go I honestly don't think it is. That being said I do consider myself very well versed in these types of games. From others who I spoke to who felt it was unfair they usually cite the reason as when you first start out the enemy has quite the superior numbers/bases/etc. so it feels like its an uphill battle. And it generally can be for 3-4 turns but the AI ALWAYS employs certain strategies that are easy to take advantage of. Once you do, it turns into a curb stomp in your favor.
If the starting disadvantage is the thing that is making this game seem difficult to some players, that's a telltale sign that they are underusing the best unit in the game, the Wagon. Not just as bait or as a blocking tool, either, but for its original purpose.
The thing about Wargroove is that since there aren't any huge momentum swings from activated powers (enemy COs are quite bad at building up meter and using Grooves when they often hang around the back line for the whole map and are easily surrounded/sniped if they press forward), on the maps where you build an army and the enemy builds an army, as soon as you match them in income, you've won. As a human player you are
always able to trade efficiently against equal strength from the AI, just because AI is AI, so once you outproduce them, you're only going to lose if you deliberately throw away units (by crashing them inefficiently against villages or letting the enemy hit them first) or by exposing your CO to a huge combined assault. If the enemy doesn't have a big starting advantage in income and/or material, there is literally no game.
And that's where the pacing problem is coming from. Players felt a vague desire for checkpoints because the first half is the hard part, and the rest is just busy-work, and a critical mistake in the busy-work is liable to frustrate them if it forces them to redo the hard part. It's quite rare in this game that late-game disadvantage (like besieging the enemy's entrenched position at home) is any sort of problem; it's only really the defence/escape maps (where the enemy has free unit spawns as a crutch) that have a sense of ramping up towards the end, instead of fizzling out in the middle. It doesn't help that the second half, when you close out the win, is often time-consuming in a way that just isn't very interesting—slow not because the decisions have to be careful, but because of the way reinforcement works and how long it takes for adjustments to your unit composition to kick in once you are on the enemy's side of the map. (AW gets around these things with better factory placement, defenders' advantage, enemy CO powers that actually trigger, transports that go around you to sneak in a surprise capture and keep you on your toes, and too many other subtleties to list.)
The first half is all the more difficult if you don't think about zone control and fail to observe that moving up as fast as possible, and as far as you are able to defend, gets you to parity quickly as it gives you room to capture everything up to the front line uncontested. Most maps are therefore easily addressed by building a Wagon first and shuttling your CO up to the furthest choke point you can handle. Capture behind the CO, reinforce the line, break through the line, and it's clear sailing from there.
To a certain degree, however, I also struggle to understand what else players are doing so wrong that they think this game is so hard. You can only diagnose it so far without actually watching them play and witnessing their mistakes. If anything, there are all kinds of things about Wargroove's systems and single-player experience that scream of insufficient testing against players with experience in the genre.
