You're not asking anyone to share, though. You're asking for the government to grant you a legally enforceable entitlement to use property that someone else worked to acquire and maintain.
So your question becomes "why should property rights exist in the first place?"
The answer is that our existence, by nature of being a human being, has material requirements. Humans have non-material requirements as well (friendships, hobbies, art etc.), but you can't dismiss the material requirements of the human experience. The same reason that it needs to be your food, your bed, your clothing is the reason that land ownership needs to be a protected right as well. If you weaken respect and protection for land ownership then, rationally, you weaken the recognition of all property rights from food to clothing to musical instruments to your tech devices. Each material "property" may serve different purposes for the owner, but that doesn't negate the necessity of owning property. And a claim to property is the ability to control its use.
> If you weaken respect and protection for land ownership then, rationally, you weaken the recognition of all property rights from food to clothing to musical instruments to your tech devices.
there's a fallacy of scale here, in the same way a handgun isn't the same as a nuclear weapon, and so should probably have different provisions applied to it. land is vastly more useful, and usable, than someone's shirt or ipad. multiple people can enjoy a stream, or a forest, or even a singular tree on a piece of land at the same time, and in a multitude of ways. that's not true of an ipad or shirt. this diversity and simultaneity of use puts land in a different class. severing tight coupling of personal property(like shirts and ipads) with private property(land, generally structures on land, though the latter is admittedly more contestable), is pretty useful and seems totally rational to me. it seems less rational to think weakening one would weaken the other. If anything, the distinction between personal and private property opens up new ways of thinking about property that can lead to agreeable outcomes. more generally, see also the benefits of the commons - https://www.nature.com/articles/340091a0
that said i'm with you in certain respects, i generally like solitude personally, but though i dream of having ten or so acres myself, i don't want to deprive anyone else of thoughtfully, carefully, and temporarily enjoying it either.
Private property has never really been exclusive. This isn't a new line that is being crossed.
"Owning" land gives you some rights over it, but not exclusive ones. It doesn't even give you exclusive right to access the land. People can temporarily access the land for a variety of legal and valid reasons like utility work, police investigations, sales, surveys, etc. They can even permanently access the land through easements.
Right to Roam isn't saying that you don't have property rights, it is just providing another limited exception to an already long list. It is saying that people have the right to enter your unimproved land for the purpose of crossing it in a way that does not interfere with the property owner's other rights. In some places it also includes the right to temporarily sleep on the land.
There is no 'material requirement' to being a human that requires that if you own a large piece of unimproved land, people cannot peacefully walk across the parts you aren't using.
You can reject one property right without rejecting all property rights out of hand (obviously. A simple counterexample: why shouldn't someone own all of the air? Are you against ALL property rights? etc..) Similarly you can reject one specific nuance of one right without rejecting others. The right of ownership (dominion) under roman law could further be broken down into the right to use (usus), to profit from (fructus), to destroy (abusus), to occupy, which can also be broken down into freehold, leasehold, commonhold, etc. It's not a silly question at all to ask whether your rights to dominion shouldn't prevent traversal by walkers etc, and your thinking on the matter seems to be quite simplistic and black and white.
To use an analogy: In the US there are fair use exemptions to intellectual property rights. That doesn't mean there's no such thing as intellectual property, or that it's meaningless.
The right to roam in some other countries is a fair use exemption to land ownership rights. That doesn't mean there's no such thing as land ownership, or that it's meaningless.
I did not. I asked why you apparently cannot enjoy the countryside without owning the part of it you're standing on. I wonder what someone piecefully hiking through your land is taking away from you, how they diminish whatever you get out of owning it.
Property rights aren't boolean, but a gradient: You can definitely grant someone the right to pass through a given area without allowing them to permanently settle the place, or go hunting.
Having said this, I actually don't think the approach you take to ownership is a good one: Humans are social creatures. We benefit from sharing, and yes, that includes food, clothing, and musical instruments. Just acknowledging that we don't live in a feudal society anymore and can share some things doesn't immediately imply revoking all property rights or living in some kind of communist nightmare.
Going back to your original post: You mentioned your biggest dream would be owning some property in the country that you have to yourselves exclusively. If you had easy access to nature that wasn't bound in private property, would you have as strong a desire to have your own in the first place?
So your question becomes "why should property rights exist in the first place?"
The answer is that our existence, by nature of being a human being, has material requirements. Humans have non-material requirements as well (friendships, hobbies, art etc.), but you can't dismiss the material requirements of the human experience. The same reason that it needs to be your food, your bed, your clothing is the reason that land ownership needs to be a protected right as well. If you weaken respect and protection for land ownership then, rationally, you weaken the recognition of all property rights from food to clothing to musical instruments to your tech devices. Each material "property" may serve different purposes for the owner, but that doesn't negate the necessity of owning property. And a claim to property is the ability to control its use.