The block reward being mostly transaction fees has happened before and is absolutely planned for and isn’t the “end of Bitcoin.”
The next two halvings probably won't cause any problems, but over the next 3 decades, the block subsidy will reduce by a factor of 256. Maintaining security against 51% attacks will require a constant backlog of high fee paying transactions. Although we've seen that happen periodically in bull markets, I wonder if that's sustainable long term.
Usage as a means of exchange has never been a strong point for Bitcoin. People just speculate under the assumption that one day the protocol will change enough to catch up with credit card latency.