The WR room is flawed. They got 3 receivers that look kind of the same. Deep threats that are undersized that struggle when facing corners that can press them at the line of scrimmage. They have a WR room with a bunch of 2 and 3’s. No legit #1. On top of that Mahomes is a trash pocket passer
With a QB the level of Mahomes, you can win with a group of WR2/3 if they all have clearly defined roles in an offense that tailors to their specific strengths. I don't think KC did enough work to create that structure within an offense that rarely fails.
For a long while now, the crux of KC's offense has been improvisation with Mahomes and Kelce (whose back-breaking plays always came in a situation where he was just "getting open" as opposed to routing somebody up), and it is catching up to them. At the end of the day, teams need an identity. KC's identity can no longer be "We can do whatever because we have a cheat code QB whose greatness shows when everything breaks down".
For what it's worth, I think Rice is a low-end WR1 but last night he was up against an elite defense that had him shook when it mattered after Pitre hit him with the Kamehameha Wave.