This is not a complaint about matchmaking. I actually think the matchmaking is pretty reasonable.
This is purely about the prizes at the end of the season. It's pretty clear division 1 is enormous compared to the other divisions, particularly the lower divisions. It's so much bigger that the 200th place cutoff for better final prizes is quite extreme. Take the accounts below as an example.
The division 9 account finished 9-3, with 11 full clears and few feats beyond the undersize and zone clear feats.
The division 1 account finished 12-0, with 10 full clears (45/48 zones cleared), and all feats except the retribution feat and 3 character specific feats.
These accounts will finish with essentially the same rank in their division. The difference is that there are simply many many more players in division 1.
As things currently stand, most 12-0 division 1 players get the same final prize as high end 7-5 players (although they do get better prizes each week). It means that once you have kyber locked, there is little incentive to try hard in the last few matches.
There is no practical reason that 4.6m players should be competing with 7m players for the same prize pool. They are playing very different games. If we split division 1 into 3 or more separate divisions, it would hardly impact matchmaking at all, or people's final league. The only result would be to bring top 200 more in line with other divisions.