Is building a basement still justified today?

The costs of a living basement are always given as a flat rate. With us, there were no real additional costs, 95 sqm of living space, the rest storage basement. Certainly, living space costs money, but many things also cancel each other out.

I think a basement is more justified today than it was in the past.
Plots of land in metropolitan areas are getting smaller and more expensive, which means if I want to enlarge my living space, often the only option is downwards. Otherwise, you quickly reach the limits of the floor area ratio, and not everywhere is construction allowed (for example, I found nothing about it in our area).

And even so, living space in the basement is not that expensive, rather even somewhat cheaper. I received price information where the price per square meter of above-ground living space was €1,650 and the price per square meter of basement living space was €950 (each plus earthworks). So you can definitely save. And there are certainly living spaces that can make sense underground.
As already mentioned, a home theater, for example, so a part of the living room is outsourced and you only have the cozy living area upstairs. Or also the bedroom when the children get older and/or you unexpectedly have one more child than planned.

So, in my eyes, a basement is perhaps even more sensible today than it was in the past, as long as it is not used purely for storage.

So, in my eyes, a basement today might even be more sensible than before, as long as it is not used purely for storage.

I would roughly claim that the price per square meter of land in some metropolitan areas is now so high that the basement, even as a pure storage space, is cheaper than providing a similar large area above ground. However, this is just a feeling; I haven’t done the calculations yet.

I don't believe there is anyone who has built with a basement and now says, nope, it actually wasn't necessary...

In any case, I prefer to spend my time above ground rather than underground. I also don't understand why everyone always wants to go to the basement for a home theater or sports...

There simply won't be a universally valid statement for or against basements, the initial situations (space, money, family constellation, clutter, ...) are just too different.

We are building without a basement. And deliberately so. I hate basements! So far, we've done great without much storage space and will continue to do so. Or rather, we have enough alternatives. A long garage where the workbench will go, a huge attic where the usual decorations and other junk will go, a small storeroom for the ironing board, cleaning supplies, freezer, and paintball stuff.
Utility room for washing machine, dryer, and technical equipment. Garden tools will then go in a garden shed.

My parents have a fully basemented house and currently could easily do without it. My father just fills up his computer den (which, if sorted and reduced, would easily fit in my former childhood bedroom). The laundry room also gets overloaded because of the dryer. The only useful part is the small workshop, which could also be outsourced to a proper garden shed and just dirties up the basement.

Among the homeowners I know, I've only met one who really uses his basement sensibly. He has his sauna and half a fitness studio down there, as well as a proper cinema. The rest really just use it as a junk room.
But like everything, it's purely a matter of taste whether you plan to add a basement.

I definitely prefer to spend my time above ground rather than underground. I also don't know why everyone always wants to go to the basement for a home theater or sports ...

It is also simply difficult if you want, for example, 4 additional rooms now. If you make the floor plan 60 sqm larger, that does not automatically create 4x15 sqm rooms, usually the layout changes completely as well.

And I find fitness in the basement better, since you almost always have the same temperature there, especially a blessing in summer.

I also find a workshop in the basement practical, since you can be louder there when the kids are already in bed.