Cryptocurrency acceptance I heard that the recommended waiting confirmation time for a bitcoin transaction is 6 blocks/ 1 hour. So a shop which lets its customer to pay in bitcoin without any waiting for confirmation would risk double spending from the side of the customer. Is this a big hindrance for bitcoin (cryptocurrency) real-life usage? If yes are there any solutions, improvements? Thank you.
In Bitcoin, it is recommended that big amount of transactions wait for 6 confirmations and smaller amounts wait for 3 confirmations.
When a seller uses bitcoins to sell he must never deliver the product with an unconfirmed tx, because since it is in the mempool it can be modified. Once a new confirmation arrives the safer it will be to deliver the product.

If you want to improve it and for example accept unconfirmed txs without fear of the double spent, you should do like what Bitpay does, have your own application to generate wallets and a transaction link only understandable by your wallet software so you can use memopool transactions.

I do not recommend you to do that, I would wait those 3 confs at least to make sure.