I felt the same way. It's not like the game is bad in any way, but it lacks anything special. I considered restarting the game with a newgame plus to try out some more interesting weapon combinations, but to be honest going back and doing it all again would feel like a chore.
Like you, I never ran out of ammo or medikits. I didn't even need to use large ones and I was on the third difficulty level (out of four). The only things I ran out of was tungsten near the start, and transducer near the end as I was upgrading my suit as much as possible. Beyond that I frequently had around 5 medikits safely stored in the safe "just in case", but whenever I needed them I could afford more any way.
My biggest criticism was the level design more than anything. It felt very repetitive to the point where my default tactic was to run to whatever corner didn't have a vent by it and wait for them to come to me.
The game was okay, but it was the worst of the three, and it's a shame because it had a lot of potential. Take Dead Space 1, add both 2 and 3's freedom of movement in Zero G, add in Dead Space 2's ability to get enemies sucked out into space using vacuums, add 3's crafting and and that's a perfect Dead Space game.
Proverbial Jon said:
My Plasma cutter is mightier than ever.
Even by the end when I could make anything I liked my default weapon was basic a plasma cutter with the rotational cuff.
I gave it stasis effect and better stasis upgrades, gave it a wider shot (but with lower clip size and speed). Then used circuits to increase speed, damage, reload and bring the clip size back.
It was absolutely killer against everything.