21M bitcoins is a lot of bitcoins when you can divide them down into mBTC, uBTC, and Satoshis.
Ah, the point is not that "there wouldn't be enough of them". The point is that if you use a deflationary currency, you won't. You'll obtain a collectible that will be hodled and that will rise spectacularly in price, and which mainly becomes a speculative asset.
I do not think Satoshi ever intended Bitcoin to be the only implementation. In fact I seem to remember that he asked for others, resulting in namecoin, before he went on walkabout.
As a first beta project it was brilliant. And it IS still brilliant, but it is not what you think it is. It is "gold". Gold is not a currency. It is kept in institutional vaults, its transactions are expensive with armored trucks and so on. And it is mainly a speculative good. It is not just a store of value, people see it as a speculative investment "that will rise". Bitcoin has all the aspects of gold. Not those of a currency. Although of course, long ago, gold was used as a currency, until it was kept in vaults, it became expensive to handle and not very practical. So people built fiat systems on top of it.
Yes, some amateurs have some physical gold in their houses. And they dare not move it. But most gold is in vaults of central banks, and other big players. Like bitcoin soon will be.
This is why there won't come a solution to the full blocks. And why it is not needed either.