The one who can issue money, can of course buy up the whole economy in the end. Whether this is by "backed" money, or "thin air" money doesn't really matter. The only advantage of "backed" money is that there will always be some finite supply of it, if the backing asset is a collectible, such as land or gold.
My analysis shows that backed money is indeed "out of thin air": As long as you have some spare asset, you can always issue money backed by them to buy more asset, and once you get more asset, you can issue more money, so the quantity of money that you can issue is only limited by the total available asset that you can buy in the whole world
To stop this kind of madness, it should be illegal to issue money backed by assets. If money can only be created by work or paying equal amount of valuables (for example exchange electricity for mining bitcoin), then that money will not create seigniorage