Even though I played CS at the highest level for the time, CAL-i, I always thought the maps were too small for 5v5 and that competitive would have benefitted from 7v7 or 8v8. That was how pubs were, and the dynamics were better. I think 5v5 won out due to practicality.
I was really involved in how serious cs was being played in 2002 or 2003, but valve did not seize the opportunity. 5v5 is the best format.
Even today, the matchmaking is horrendous and toxic teammates ruin the fun.
When you solo queue, individual performance is ignored, so you must carry your whole team if you want to gain rank.
The game is great but generates too much frustration for me.