“If the whole world uses bitcoin, then there isn’t enough room on the blockchain for everyone to use it. Seven transactions per second is not enough. <Insert favourite altcoin scam here> is better because it scales.”
To understand why this is misguided, first, you must understand that not every transaction is required to be final settlement and recorded on the blockchain – in much the same way that not every transaction in dollars is settled with an exchange of physical cash between parties. Looking at it like that, not even dollars can scale for today’s economy!
Bitcoin transactions can scale virtually limitlessly with the lightning network. The more people that use it, the greater it scales. In the way that emails can be sent around the world without regard to scaling issues, lightning payments will be the same. Lightning actually scales many orders of magnitude more than VISA, which will open new possibilities, like streaming micropayments, and business opportunities.
The sound-bite about Bitcoin scaling is “seven transactions per second”, although it has improved a bit since Segwit was activated in 2017. Large transactions which include individual big payments, or aggregates of many small payments, or the opening and closing of lightning channels, is actually more than sufficient at seven transactions per second.
I don’t know how many armoured trucks per second deposit cash/gold to banks vaults, but I suspect it’s a little lower than seven per second!