Not exactly easy to fire someone (even with reason) in some EU countries due to (in some cases very needed) regulation.

This is very true. I have known people truly shit at their jobs. They've done things I would assume to be the final nail in the coffin - and some how they just trundle along frustrating everyone around them. WFH and you can easily get away with under performing by 25-50% in countries with strong protections for employees.

The point is that when you're not slacking, no one should care. But now they do care because its a war.

It's only "war" because people's ego is tied up in their work because they make it their identity, and WFH challenges that, very similar to people who brag about 60-100 work weeks like it is a badge of pride. Some work to live, others live to work, and there is a whole lot of inefficiency to be squeezed out that is hard to squeeze out because of the lizard brain [1] [2].

It would be great if it wasn't a war, just measure output or equivalent objective measures, but like religion (which wars have also been fought over), belief systems die hard. Mental models are rigid, emotional health is not always available to everyone, and so on. Loss of third spaces doesn't help, and your cohort of workers who demand in office time because that is the only socialization they get (or those who are fleeing their home life by going to work) also contribute to the friction.

[1] https://en.wikipedia.org/wiki/Bullshit_Jobs

[2] https://en.wikipedia.org/wiki/Parkinson%27s_law

An interesting point, I think I can add that those who know have no need of nice offices, dresses, titles on business cards and so on to "show their identity", while those who do not need them to fill the void. And that's might be a nice "large raw measure" of those who need to fill the void, so they like the office, and those who not. It's an imperfect measure of course because on both sides some are on the opposite classification but it still work in the mean.

Similarly someone who do work less at home typically is someone who can't be productive anyway, who sell his/her own time/presence but not much competence, again that's not always true but I'm pretty confident it's true in the mean.

However the real war is not about being remote or in person, but live in cities vs live outside, because with WFH as the way to work for all eligible jobs the big of real estate go bankrupts quickly, similarly many bit tech service player like Uber, Just Eat and so on, together with the cloud+mobile model. The rest is marginal.

Some do like the office because they have tough familiar situations and being "separated" for a significant part of the day means for them have a way to keep their family, witch sounds good for them, but IMVHO it's just a way to torture themselves more, some other do like the office simply because they can't afford a good home and they have a better setup in the office, again it's not a good thing to have IMVHO but all such examples are marginal.