Actually, much harder given the pressure involved.

You don't have to go to the bottom of the deepest part of the ocean, any more than you have to have a space colony in the hardest parts of space to colonize. You can have an undersea colony in places where the pressure is modest and there's still sunlight.

But no one does, or has tried to, or has any plans to. Because it's not worth the difficulty. Just because something is really hard to do doesn't mean it's worth doing, any more than the converse.

Welp, that's certainly a take. For some folks it was too hard to set off and look for land in the New World and for some it was too hard to expand the United States out west. But exploration (and more to the point, the spirit of exploration) drives innovation and the problems you mentioned will eventually be overcome.

Except it's fairly easy to articulate the benefits of looking for land in the New World or exploring the United States out West. Getting more developable, arable land for cultivation and settlement is generally a valuable thing. Any land on earth that's capable of supporting human life can generally be settled, and have value for the settlers.

The same is not true of space, any more than it's true of the undersea floor (even in shallow areas). It's not worth it. You don't gain enough value from having that extra area of habitable land to make it worth the effort. It's always worth exploring those areas, but not worth maintaining a permanent human settlement with babies and children and such.