What are you on about ?
Of course no more land is being created, actually climate change means it is being destroyed. This does not mean it is an asset class like no other.
Things like fine art, classic cars, etc., are “investments” because they aren’t making any more Van Goghs or 1960s Ferrari’s. That is an asset class almost exactly like land. Though the painting is rather less functional.
How about more traditional asset classes like, for instance shares. Funnily enough companies don’t issue new shares just for fun. Many companies have a fixed number of shares over many years. These assets rise and fall with the fortunes of the company.
Sometimes the shares are split, which is the same as splitting a piece of land into two. Each half is worth, roughly half what the whole piece was.
You are making a category error. Investment asset classes are characterised by having a fixed, or nearly so, supply. If companies could just issue as many shares as they liked at any time the shares would be worthless. See also, money.
Assets and commodities are completely different things. A commodity, a mobile phone say, has a more or less completely flexible supply. A mobile phone is not an investment asset.
That the land is all owned already does not prevent it being a free market. Anyone who owns land can choose to sell it and anyone who can afford the price can buy it. Just the same as with shares, gold, classic cars or anything else.