Should there be a city in every country where everything was legal without limits and people could do whatever they wanted all the time, but once someone enters, they can never leave?

What does "legal" mean?
If there are no laws or no enforcement, the city's strongest or most ruthless inhabitants will make and enforce their own (but without bothering to write them down or give you a fair trial).
Cities like this exist, plenty of them. Everywhere a state isn't strong enough to enforce the laws, gang rule takes over.

Hey I heard about a bunch of men that want to be going their own way, maybe that'll be a nice spot to put those people

glances at OP's instance name

It sounds fun and all until billionaires and their militias enter the game.

On paper I could almost agree but let them leave ONCE. By agreeing to follow the rules and laws of the society etc. And if they then break the agreement, permanently send them back. This makes it so that people born in there have a chance to leave. And perhaps some people could have a light bulb moment that maybe having institutions in place isn't all that bad.

That said, you always have total freedom to do exactly what you want. As does everyone else - that's the part everyone tends to forget when floating ideas of this type. It's just that majority of people already have decided to use that freedom to create systems that encourages certain behaviors and discourages others. People who want absolute freedom for the individual often seem to like the idea of stripping other individuals from the freedom of forming collectives.

We already live in a society that's the result of the jungle's law of total freedom. The only issue is that you can't choose what kind of a system you're born to and it's not necessarily easy to switch into another system. But you always have options. People just tend to want to have their cake and eat it too.

It's called a ghetto, and those already exist.

What about children born there or other people taken there against their will?

Also, as other have pointed out, no externally imposed law just means people will organise and internally impose laws, and boom, you have laws again.

Umm no there shouldn’t..

I suggest you play cyberpunk 2077 to see what happends in a city with almost no rules. The idea seems good in theory, but falls flat in practice. such places would have enormous allure, when announced hundreds of thousands would trek there, in the hopes of striking it rich through less than ethical means, companies and facilities would thrive since minimum salary is just a suggestion. These cities would become economic powerhouses of depravity. With power comes influence and slowly they will try to infiltrate the government that is supposed to uphold the law in the rest of the country. This is even further accelerated because people go where the money flows. Populations grow, the city grows, economy grows and degredations continue. This cycle repeats until there is no difference between country and city.

Why on earth would I want my tax money to go to that?

No

I Just put a question mark at the end of this sentence, so therefore it's a question now?

This isn't a question?

You ever seen the film Gamer, remote control convicts. This is how you end up there. Cameras everywhere and everyone is tagged, watch to see if your favourite survives people!

South Sudan simulator.

Sounds like the perfect location for a bioweapons lab