I could take or leave sprinting.
The only Halo game it really harmed IMO was Halo 4, cause there was no opportunity cost for using it like Reach, and no penalty for using it like Halo 5.
Infinite's sprint in particular is such a small boost in speed over basic run speed. It's a nice help when you need to go a decent distance to catch up to your teammates off spawn, but it's not a fast enough increase to get away from a player that's running after you while shooting. I don't think the game would gain or lose much by getting rid of it honestly.
Haven't had much issue with spawns. Halo (specifically Slayer) has always been about teams pushing to spawn and flipping the map. I guess if they made the spawn AI a bit more aggressive about flipping the spawns sooner, you'd get 'safer' spawns, but you'd also have more time taken by players/opponents finding each other, which slows the pace of matches down.
My biggest issue with the game remains the maps. As I said before, I don't think there are any real stinkers - other than the 1-flag map when it's used for any other mode - but there aren't really any winners either. They're all a solid 6 or 7 out of 10.
When I think about Halo memories, the maps are the first thing I think about. The list is too long to go through from CE to Reach, but for example, I could play 1-flag on Zanzibar/Last Resort or CTF on Valhalla for HOURS. And did. Many times at the expense of schooling, lol.
None of these maps anywhere near as iconic, in any mode. They play well. They flow well. They're very fair and competitive without being simple mirrored or 3-lane layouts. Which is great. But there aren't any legends in this lineup.