I emphasize that altcoin projects have smaller total supplies than Bitcoin total supply and literally they are more scarce than Bitcoin in supplies. However, it does not result in any higher demand on such altcoins because they are very useless projects. Useless means no value, no value in turn means no demand, and price consequently must be low.
Yes, there are many altcoins with even more scarce supplies than bitcoin and it is not difficult to create altcoins with such fixed supplies.
Supply is also an important factor but it is meaningless if it does not attract people and there is no demand for it. So don't focus too much on supply, but pay attention to the use cases and applications that the asset brings.
First, we need to identify and care about the use cases and their needs, and if they meet those criteria, then we will look at the supply. What makes Bitcoin different from other assets is that it is decentralized and focused on providing privacy and freedom, something that almost no other asset can offer.