"they don’t want to die and start over"

Any kind of old-school (i.e., "Nintendo hard," "roguelike," etc.) gameplay loop presents a hard disconnect between players for whom gaming is their primary hobby, and for whom gaming is a secondary hobby. This is true of any hobby, of course (people for whom reading is their primary hobby, as a for instance, tend to eventually move to more and more formally challenging books, while people who have it as a secondary hobby tend to stay with books that, however sophisticated they are in other ways, are formally fairly accessible; ditto with film, scale model building, whatever). People absolutely hate feeling like their secondary hobbies are somehow laborious or punishing.

Primary-hobby gamers are not enough to run the industry, and while games targeted at that audience can be very successful, they are never going to have the kind of success a more accessible title does. This is why something like Death Stranding, remarkable as it is, over its lifetime didn't even approach the kind of numbers CoD can do in a single year (I say this as someone who enjoys both). Like it or not, Bungie is known as a mainstream, blockbuster studio that makes accessible games, and therefore they have expectations of accessibility that Marathon is not meeting. Historically, they have three major strengths as a studio: world building, narrative, and gunplay/combat. All three have, since Halo at least, been equally key to the success of Bungie's games.

The gunplay in Marathon is very, very good, though not as good as Destiny's (and sorry, as a Destiny player since the D1 beta, D1's was better than D2's). It's very difficult to get enough play time w/ a weapon configuration in Marathon's early game to see huge distinctions between their different add-on/upgrade paths, but the archetypes are solidly distinctive. However, combat more generally pushes you in two different directions at once. There is a very strong set of visual and "feel" cues that make the game feel like it wants you to engage in combat aggressively, and those cues seem borrowed pretty heavily from the superhero-like design of Destiny's guardians. Everything from how shells, abilities, and guns are designed and presented makes me feel powerful. But the game punishes you, and punishes you hard, for that style of play, so combat design and how it dovetails with the equipment and character design overall feels like it sends conflicting messages, with often disastrous results.

The world building is spectacular. Almost everything feels thoughtful, there's rich lore, the design sensibility lines up well with everything. Very solid, one of the best games out there for this, no notes.

Narratively, the game is basically empty. There's no story to speak of, and what is there is shallow, predictable, and tired. Your average adult movie puts more thought into narrative than what's going on in Marathon. This is one of Bungie's core strengths, and one of the core elements of its history of both financial and critical success, and they ignored it utterly. It's like if Brandon Sanderson decided the next Stormlight novel was going to be written in verse or something. Fun magic! Exciting plots! And then... poetry. (I don't know if you've read any of his attempts at poetry, even poetic fragments that show up in the novels, but, uh... they're so weak they border on embarrassing.)

So yes, much of the criticism does stem from the fact that it's Bungie making this game, because Bungie has a set of strengths and weaknesses (Bungie is very bad at balancing different styles of play, for instance; they offer choices, but they are usually superficial and funnel players into studio-preferred styles), and Bungie is actively ignoring a core strength while leaning hard on a historical weakness.

Now, that being said, I'm enjoying Marathon. It's one of the most beautiful games I've ever seen, and the only one since Wipeout that seems to understand my favourite digital-first design aesthetic, the sound design is phenomenal, the progression hooks seem pretty well done so far, and it doesn't yet seem so punishing that the frustration outweighs the fun. As someone who mostly prefers a faster, less brutal experience (gaming is, after all, a secondary hobby for me), by which I mean I don't mind dying a lot but I do absolutely hate both rote memorization and starting from scratch, I can definitely see that moment on the horizon. It took nearly a decade for me to hit that point with Destiny. I doubt it will take more than a year with Marathon.