What's the ideal level cap for an MMO?

Massively commenters recently debated whether a game without levels is the same as a game without a leveling cap thanks to Black Desert's proposed character advancement system, an increasingly common lateral advancement system that allows players to build their characters more sideways than up. But outside of such sandboxes, most themepark games stake their mechanics on levels, for good or bad.

And that got me thinking about the ideal level cap for an MMO. Even if two games require roughly the same amount of time to cap, a bigger number can seem so much more intimidating. Asheron's Call's 150 levels and Anarchy Online's 205 always seemed unreachable to me, and wasn't it cute back when World of Warcraft expected but 60 levels out of you?

What do you think -- what's the ideal level cap for an MMO with levels?

TH

30 plus some sort of ascension level system after that for horizontal progression in gear/abilities etc.