Here is the biggest problem with cryptos that no one is focusing on
If you want to sell digital goods or if you need a notification on your shop that client made payment you have to use a third party or a node or a smart contract
This is not true. You can search for free any block explorer to see if the payment happened.
And many wallets notifies the user when he receives credits.
Electrum (from electrum.org) shows a popup in the desktop when I receive a new transaction. I can almost guarantee that it does the same in mobile version
https://electrum.readthedocs.io/en/latest/faq.htmlThe client subscribes to its own addresses (nit: sha256 hashes of scriptPubKeys)
so that it would be notified of new transactions touching them. It also synchronizes the existing history of its addresses. This means the client sacrifices some privacy to the server, as the server can now reasonably guess that all these addresses belong to the same entity.
Your "biggest" crypto problem is a just a bad software you are using.