No they use the same engine. It's more like they're trying to include all the guns etc. from Vanguard in Warzone which makes things messier. It's always buggy after a big new content drop, unfortunately.
My take all along was that Halo isn't that good. Why would I want to justify an MS game not being good? Two of my favourite games this year (Psychonauts 2 and AOEIV) are MS games. I have a Series X and Gamepass on PC for feck sake
I just don't find Halo to be that... exciting. I appreciate it for what it is but multiplayer FPS games have moved on and it's not quite up there for me. I think I'll enjoy the campaign a lot though, been ages since I played a good FPS campaign (DOOM I guess).
Warzone can definitely be spoken about negatively, just check the thread, I moan about it all the time, it's far from perfect, as I said. My point is comparing it to Halo to make Halo look good after it just got a big content drop is silly. You can't accept the stupidity of comparing the two, that's fine, you're blinkered by your love of all things MS and think everything they shit is gold, good for you. I'm not the one who started comparing them, if you are going to criticize another popular game then it's only natural to expect people to call you out on it.