Pales in comparison to the likes of Hollow Knight, Steamworld Dig 2, Celeste, Super Meatboy, VVVVVV, and Deadcells. Hell, even the End is Nigh, which I wasn't personally a big fan of, was a better experience than The Messenger.
This game can't decide whether it wants to be a linear, challenge based platformer or a metroidvania with light (and I mean light) puzzle elements. As a result it spectacularly fails at both, making for a lukewarm gameplay experience.
Poorly thought out level design is the biggest issue holding this game back from greatness. During the linear section of the game, each level feels all too easy; this is because, unbeknownst to the player, each level is actually meant to be traversed multiple times in a metroidvania-esque fashion. Because of this, the difficulty for each individual section must be kept low so that backtracking through them isn't a chore. However, there are occasional challenge sections, which makes sense for linear level design, but are a complete pain to backtrack through.
Backtracking in this game, in general, is a pain. The game is split into levels, which are split into linear segments, each of which having exactly one entrance and one exit (with a few exceptions). This sort of design is not conducive to "metroidvania" style of backtracking, but these devs REALLY wanted backtracking. So what did they do? They give us a hub-like zone halfway through the game, at which point you're tasked with solving some mildly cryptic riddles which point you towards going back to certain levels. This hub gives you the option to use, in a way that I can only describe as snide, fast travel portals, but only to a select few levels, which artificially forces the feeling of metroidvania exploration. What I mean by this is, say you need to go check out zone 1 again, well the closest we can warp to is to zone 2, so great, let's traverse through zone 2 -> zone 1 and find what we needed. Now let's go back to the nearest zone 1 checkpoint, and guess what, we can instantly warp back to the hub-zone! That's right, every checkpoint allows for one way warping back to the hub, which just feels inconsistent and contrived given the way the hub portals work. Unfortunately, this is the style of "exploration" that the game offers. It's neither fun nor engaging.
The only difference between the first time you run through the levels and the backtracking portion of the game is that a few of the rooms are slightly redesigned and offer tangential mini-platforming sections to go through. These new paths almost always lead to a dead end containing one of the collectables (which are used to unlock a certain something that turns out to be completely underwhelming).
Don't get me wrong, I loved the basic gameplay mechanics, as they allow for some really interesting gameplay challenges, but it's as if the developers were too scared to actually design obstacles that specifically take advantage of these fun, and potentially deep mechanics (except for the wall jumping/clinging mechanic, this one needed work—the fact that you auto cling to walls the second you brush against one instead of just sliding down them is a baffling decision to me; it feels bad and completely ruins the flow of gameplay. You can't even release from the wall in an intuitive way. One would think that simply pressing in the opposite direction of the wall would let you let go from it, but no, you either have to jump or hold down and jump. The only reason I can think of why they kept the wall climbing mechanics like this, rather than some sort of variation of Celeste's incredibly well-realized wall climb mechanics/control scheme, is that the auto cling makes some platforming sections easier, despite the fact that more often than not it just gets in the way of playing the game).
Another complaint is that there are almost no platforming obstacles that actually require the player to have any sort of mastery over the game's mechanics. On top of that, the game has an inconsistent difficulty curve and is plagued with awkward checkpoint placement, cheap deaths due to off screen hazards, and boring/un-fun boss fights (who are the biggest offenders of the inconsistent difficulty. Oh, and don't forget the random, incredibly tedious SHMUP boss fight that comes out of nowhere).
I personally can't recommend this game. The visuals are fantastic as well as the OST and humorous writing, but that's it—speaking of OST, the sound design in regard to gameplay was bad; there were no sound cues for moving obstacles/platforms, making timing your movement entirely dependent on visual cues. It sounds like a minor nitpick, but good sound design makes for more natural and intuitive gameplay.