I am happy that you figured this out by yourself, and if I am asked, I would say that the 21 million BTC total supply is even too much, the lower it is, the more the law of economics on demand and supply over the price would be enforced. The goal of the 21 million supply was to create scarcity, but till now, the effect has never been felt because you can easily get your Bitcoin today. I wonder where the price would have been if it were difficult to get Bitcoin and everyone held on to their Bitcoin.
That will naturally create more value!
Altcoins can have lower total supplies than Bitcoin and they can be Bitcoin forks or shitcoins.
In a situation like this, you balance the economics, you don't just talk about the supply, you have to balance it with the demand. Fine, some altcoins have some lower supplies than Bitcoin, but do they have the value and demand of Bitcoin? That is what you need to look at.
I don't even know why you are particular about altcoin when Bitcoin is the subject matter. Altcoins should shut up when Bitcoin is speaking, because they are mere imitations, and will never follow the same economics and dynamics of Bitcoin.