100 GB blocks is politically unrealistic in the foreseeable future but technologically not really, especially because network and storage continue to get better and cheaper even if CPUs are stalling. Nodes don't need to store the full chain, and 10 years of that size of block would only be about 50 PB. Gigabit networks are only becoming more and more common, a 1 Gb connection will let you get 75 GB over 10 minutes (and using the math from the wiki you only need 0.76 Gbps to handle 200k tps). Also not every node needs to see every transaction, the effective bandwidth can be much lower, just like the effective storage.
And as the wiki points out, PayPal has a much lower TPS than Visa or others but is still widely used as a direct consumer-to-merchant or friend-to-friend payment system. In addition, the better straw argument against Bitcoin as a payment system has always been "who is going to wait 10 minutes on average, sometimes much longer, especially if you want the gold-standard 6 confirms, to buy a stupid pack of gum?"
The whole point of SEPA transfers was to move all transfers to be cleared directly via the main ledger, in a matter of seconds, across different countries and currencies.
If Bitcoin is inferior to an existing payment system used by 500 million people, then it’s worthless.
If Bitcoin is strictly inferior to an existing payment system used by 500 million, then it's worthless.
IMO the major value proposition of bitcoin is that no one can exert influence to invalidate tx or blacklist certain users. Payment systems that have this property will always have some utility for organizations that nation state actors are trying to stop, e.g. ransomware, any darknet market provider, political dissidents, freedom fighters/terrorists, people trying to participate in a market in a controlled economy etc.
Most importantly, though, it's decentralized. It's simple to implement a fast, centralized currency and payment system. But Bitcoin's main attraction is that it values decentralization greater than efficiency and throughput, thus making it, primarily, a store of value, as opposed to a means of payment.