In previous Halo’s there were Account levels, like Spartan Ranks. Levelling that up gave some sense of a goal, bragging rights or fulfilment when completed. In Infinite, sure there are the Battlepass levels, but that in no way reflects the player’s level as you can just buy your way to max rank immediately.
While the battlepass system is fine (exp issues aside), it doesn’t mean much other than the freedom you have by choosing to customise your spartan with everything you’ve unlocked. With Spartan Ranks, you could brag about it and if you were at the max rank, like SR152 in H5, you knew you were among the most dedicated players.
Commendations were fun to level up and gave you some sort of goal in individual matches without pressuring you to fulfill them. e.g. the Phaeton Gunship Gunner commendation gave you an incentive to kill people in the Phaeton, but besides the exp rewards (which you also got for completing games), there was no time pressure to complete it, and therefore far more fun that these Battlepass challenges we have now.
Medal tracking was also great, while it didn’t mean much, it was still some sort of bragging right by showing off how many Killionare medals you got. In Infinite, you can get those medals, feel good about it at the end of a match, but besides looking at your match history and finding where you got what medals, your achievements are lost to time, and give almost no incentive to keep it up.
All in all, I love Infinite’s gameplay (even if there are a few things from H5 that I miss a lot), but the lack of personal stats, levels and permenant challenges (commendations) feel like there’s no incentive to play anything outside of ranked.