The teams are not forced to take the budget cap. Teams that elect to take take the budget cap gets more technical freedom. Which is the problem with the bigger teams.
The way I see it, the big manufacters (Ferrari mostly) does not want a even playing field. They want to continue dominance in the sport.
I guess I'm one of few that would like to see a two tier type racing.
Small team with more tech freedom against bigger team with unlimited budget race.