In theory it scales as much as you want it too, but in practice it creates problems. There are tradeoffs for making a trust-less and decentralized system that consumes a lot of bandwidth and disk space to scale.

In anonymous/private coins, the scaling debate was much further ahead because their mixing or zero proof systems create much more bloat that have the potential to render their blockchain DOA - even while having tx volume like 1% of BTC.


There is no bottleneck if you pay a bit more. The fees are pretty decent, even for top priority, for a "crowded" block anyway. If someone wants his dust to move at once though, by paying peanuts, let him wait.