Campaign:
Story writing is pretty bad, between plot inconsistencies and killing certain important characters offscreen. Plentiful glitches that ruin the fun of speedrunning, repetitive and obvious copy pasted map design. Lacks the beautiful wide-shots of previous Halo games, opting for an empty feeling open world format. Random enemy encounters in the open world lack incentive/rewards for fights, and are much more easily avoided. Bosses exhibit poor ai for engaging gameplay and boil down to being bullet sponges, increasing the difficulty setting only amplifies this poor design choice. Most of the soundtrack bleeds together as fairly generic, with exceptions like the title theme which is just a recomp of Martin O'donnel's work from previous Halos, the original compositions from Infinite are comparatively lacking. While initially fun, the gameplay loop gets stale and repetitive. Weapon sounds are generic and lack weight and distinction seen in previous games.
MULTIPLAYER:
While initially engaging, the lack of content seen in previous games (forge, customs, gamemodes like infection, maps) is disheartening. The desync bugs from poorly maintained servers are as plentiful as the non-stop microtransactions. Vehicles are poorly balanced and get shredded easily, overall there are less weapons than in previous games. There are ALOT of bugs and exploits that need work, but 343 seems to focus on adding more microtransactions than fixing them. Having to pay for armor colors and not being able to earn them through progression removes a large motivator seen in previous games. Many staple Halo features have been removed and marketed as microtransactions (even to people who paid for the campaign)
Effectively making Halo fans pay for less content than previous games.
While the option for changing this broken system remains, 343 has shown a poor track record when listening to the fans and continues to milk the community through microtransactions instead. Microtransactions were a huge problem with Halo 5 and Imfinite is no different. It is unfortunate but Infinite appears to be a shameless cash-grab, lacking the integrity behind it that was seen in previous Halo games.