I see your point, it makes sense. Many support in a similar manner that the European Soccer cup (UEFA) is more competitive than the FIFA World cup because the teams are on average stronger.
Still, what should be measured to my mind is "Given a specific team (any in the world), what's the probability of it winning the event ?", and then you average over all teams.
I also think in this regard that Masters = Champions, but if once you take into account that it is harder to get to Champions in the first place, then winning it is less likely whatever the team. That's what makes it "more competitive" to me.
The "paradox" is that although more teams in the event means weaker opponents on average, it can still only decrease your probability of winning. The reason is that on top of not being upset, you also still have to beat the good teams at the end of the tournament.