How can Bitcoin grow if new users are not allowed to join this crowded bus, my logic is powerless to find an answer. Who can?
You are believing a shitload of propaganda, if for some reason you are buying into the idea that the bitcoin bus is full.
That's totally nonsense. One thing is if you want to buy coffee with it and you expect total resolution of transactions in seconds (which bitcoin is not there yet), but another thing is if you want to store your value securely and to use bitcoin for it's best features - value security.
In any event, there's all kinds of room for you, your friends and a multitude magnitude of others to jump on board with either today's current capacity and/or with various ongoing developments that will allow even more peeps to jump on board and to increase various kinds of quicker transactions.... .
There is no need to believe anyone, you only need to look at the mempool. I don't suppose Bitcoin will end as peer to peer cash to buy coffee, rather a convenient cross border value transfer vehicle. Other currencies will satisfy the pay for coffee demand much better.