I think you're gonna run into that old joke - ask two economists about something and you get three different answers - because it definitely varies by person. My opinion is "build the environment you want, and modify it however your regular play group wants if that stays within your tastes". Onder's got the right idea, IMO, because the flip side of "put the themes you want in your cube" is "actively exclude the ones you don't want"!
Now, that said, here are far more words about my specific position:
I have definitely aimed
against control/aggro deliberately by weakning them, specifically by removing individual power outliers. I have
a higher power level cube than most here (summary: 450, no power/initiative/monarch, yes
Natural Order) but cut both
Murktide Regent and
Ajani, Nacatl Pariah for broadly similar reasons. I'm fine with
Torrential Gearhulk and
Thalia, Guardian of Thraben, but I want people to have to work for it.
For control, that's "work at killing your opponent" - if you can get a
Jace, the Mind Sculptor ultimate off, you deserve the W. But the combat-based-murder options are deliberately possible to kill (not
Aetherling) or reasonably-sized (not
Murktide Regent) or stuff like
Saheeli, Sublime Artificer that has a lot of upside but still works via combat. Also consider keeping all your wraths at 5+ mana* or conditionally-effective or similar.
For aggro, that's the other side of "work at killing your opponent" -
Ajani, Nacatl Pariah is cracked, like
Broadside Bombardiers and
White Plume Adventurer and so on. You have to put in a little more effort than
that! Even though I'm gonna let you have
Cecil, Dark Knight or
Bristly Bill, Spine Sower or whatever, there's still a line where I just kind of go yeah, too efficient, not worth it. Rewarding synergy over raw power helps with this, but there's also different
kinds of raw power.
Thraben Inspector is more powerful than
Savannah Lions, even against a control deck, but it kills substantially more slowly! Stuff like that.
*this effect will forever be known to me as the "kithkin shotgun", memorably depicted by paz of Pro MTG Online fame over a decade ago: