I think there's a difference between wanting Halo's visuals to stagnate and wanting Halo's visuals to stay true to what came before.

If 343i had replaced the rocket launcher with an equally offbeat and distinctive weapon, you'd probably hear a lot less complaining. Since the replacement wouldn't look out of place in CoD:MW, you get complaints.

No, they Hydra doesn't count.
And on that subject, I probably would have named it something other than the Hydra. But that's so low on the complaints list, we'd be in paradise if it made the top ten.