Would this be a good idea to begin with? I was hired at a startup where it was specified to be remote (only the U.S. state was listed). After a few months, people in the area closest to the office were mandated to come at least 3 days a week. I feel it is somewhat unfair that people who live elsewhere are able to stay fully remote, even if I like being in the office.
You are going to get absolutely nowhere with this complaint except making yourself look like a whiner.
If you have a specific constructive suggestion on how to make the commute or office more attractive -- maybe the company can cover public transit passes or at least arrange for discounts on them; start an after-work lecture series or host user group meetings or something like that, get the cafeteria back into operation -- those may be worth bringing up, but most of those should go to the site manager if there is one and they can then talk to the CEO about funding.
Unless your contract said the job would always be remote, you should have expected that the company could, and probably would, eventually want you on site, and the easier that transition is for you the sooner they would request it. Remote work, even in normal times, is an idea that goes into and out of fashion on the whim of management, and it's one that managers at all levels, and across levels, of a company feel differently about.
It could be much worse. They could be telling you that they wanted you on site at a location 200 miles away, and you had a limited time to either agree to relocate, find another onsite position in the company that would let you continue living where you are now (if there is one, and with no assistance), or be dismissed. Or something similar, though that's a real example. That would be worth asking the CEO to reconsider, though "fairness".is not a good argument there either.
Unfortunately sometimes it's necessary to fight for the privilege of remote-work. If you like it and value it then you should stand up for it. That's why I disagree with the other answer. We can't complain about not being able to work entirely remotely and not do anything about it.
So yes, you should express your concerns, but not once, but in every occasion. That's the only way people don't forget it and won't say later that it's no longer an issue because everyone got used to the new old office arrangement. If this happens, it's over.