Why there's no separate Rush or Breakthrough mode?

It was a reason for me to quit 2042 every time they removed a fun gamemode, you had fun for 1 week then had to go dormant till you got lucky on the gamemode selection

there was an atk/def gamemode the other day, rush and breakthrough. One is 12vs12 the other 24vs24 how is that even considered to be a similar gamemode.