What? This is like taking the first game of a kind ever and claiming it's bad because it doesn't have what the evolved doom-clones have. Ok, it's not the first, there was wolfenstein before and maybe few others, but the first with more complex engine that started also the doom-clone craze. And I don't think gunplay was bad, in fact I still play and the gameplay holds up well (nothing like mowing tons of monsters coming to you), I still adore the sprites and texture design, they might be low detailed for today but were really good at the time, also the level architecture still works very well. That's my opinion, the fact that at the time all these elements where more than well done for the year being and that it's still playable with modern ports if one wants jump and mouselook and all that.
In fact, I thought that the Marathon series were overrated (and that's how I discovered this forum), because I never played Marathon when it was released at the time (I never owned a Mac). So, many years later into now, I discover that there was this game which people say was revolutionary, much better than Doom at the time, and it was called Marathon. So, I was curious to see it, and see what happens when you see it now under modern eyes. My first impression was that the weapons, enemies, level design, colors and all that are too bland. If the levels were designed as a 3rd party MOD for Doom, I am sure many reviewers would give negative votes because of how bland and uninteresting the levels look. It even reminds me some later mediocre doom-clones of the era. I am not trying to say it's bad though, I am saying that after hearing from Marathon fans how underrated it was and how it was so much better than Doom and a hidden gem and all that, I failed to see what's the fuzz about it, but maybe because I never played it during it's time. Maybe that's how you feel about Doom, you were born with Marathon, but never cared about Doom at the time and you see it with modern eyes and can't appreciate.
I do want to play it though. I want to see history. I don't get the fuzz yet but maybe I have to play further. The innovations I hear is that it really was the first game with mouselook (Not Quake, neither Terminator Future Shock too) and also featured some kind of scenario, terminals with story, maybe more, I really have to try to like it to play further and discover what it did right. So, these were improvements over Doom, but I am not sure if they hold so much. I played other really improved games like Duke Nukem 3D (so many innovations over Doom, so much interactivity you don't even see today) and Strife (great use of Doom engine, dialogues, missions, changing environments, great atmosphere, three finale). I will give it a shot though if I find out how the hell I can invert mouse in Aleph One port. It really gets me motion sickness now, it's now how I am used to.