If you think leafy greens are only good for making a profit, then you're the one who's wrong. Nutrition is about more than just calories. Someone who doesn't get enough calories gets malnourished, someone who doesn't get enough nutrients gets malnutrition. It's two different things. Vegetables are necessary and you can't just write them off, much as you seem to want to.

Also, a vertical warehouse operation has multiple stories and can have panels mounted all up the southern face. You don't need to have an entirely horizontal solar farm, so no it doesn't quintuple the land you need.

And yes, eliminating meat from the common diet can help to rewild arable land, but that's a completely separate conversation and not an argument against warehouse agriculture.

Saying there's no shortage of land to feed 15 billion people is irresponsible though, because without any major changes to the way things are done, feeding 15 billion people would absolutely result in more habitat destruction.

And why grow your vegetables and fruits and strawberries far off, or in a bunker, when you can build a million local greenhouses in your community that could additionally serve as food gardens or parks in colder weather?

You don't seem to understand the issue at all. Building a million "local" greenhouses takes up space. Each greenhouse has a footprint. The millionth one over won't be very "local."

The point of warehouse farming (rather, one of the points), is that it can be done in urban centers where there's no space for greenhouses. It's literally a solution for food deserts and transport costs associated with the majority of food being produced in rural areas. Warehouse agriculture brings food production closer to population centers. I've already pointed that out multiple times and you just seem to ignore it.

If we ever find a way to split water into hydrogen directly using fusion we'd be set.

That's not what fusion is at all. I've already corrected you on this, which you also ignored.

Nuclear fusion is when you take two atoms and fuse them into a different kind of atom. The simplest form is making one helium atom from two hydrogen isotopes.

It has nothing to do with "splitting water into hydrogen." We can already do that. It's called electrolysis. Plants need more than just hydrogen though, so I'm not sure what your point is there.