Opinion: 6 members per team has hindered the progress of competitive Overwatch
Most games, like Dota 2, LoL, and CS:GO, have 5 players per team.
With 6 players, a team's salary and living expenses go up by 20% immediately.
Imagine if there were 1000 players per team. This team would not be sustainable at all because the revenue generated by each team is largely independent of number of players (streaming could help and player-branding could help), but the expenses are directly dependent.
In the E-sports industry, we know that all but the top organizations don't really make any money. Add in this extra 20% expenditure pressure, and you have even poorer growth.