I don't agree with your first three points, not that it matters. But to me the Bills were out coached on both sides of the ball. The gameplans were lacking and any adjustments did not work. The Chiefs scored on every meaningful drive other than the first drive where they had a drop. For me the game was not closer, it was probably worse than the score with the gift TD in the first quarter making it closer.
One TD would not have changed much, if the Chiefs needed more points they would have had little trouble getting them. The Chiefs just had a great gameplans vs the receivers and the Bills did not counter it. Allen should have run it more since they were playing man and more passes/checkdowns to the RB's and TE's on schedule may have gotten them out of their scheme. We needed to counter punch but had nothing.
On defense, they did a decent job against the run but apparently to do that meant they just did not cover Kelce. On Hill's long RAC play, they could have tried to tackle him near where he caught it but instead they just kind of watched him run. They got little or ineffective pressure on Mahomes, Epenesa ran past him like a fool on one play.
Bottom line, the were out played on both sides, a play here or there was not swinging this game.
I agree with 4 and 5. The Bills needed to counter what the Chiefs were doing defensively, taking away the WR's. Run and thrw to backs/TE's on schedule would have helped get them out of that.