network congestion leading to huge confirmation times
This only happens if you don't know what you're doing.
and lack of scalability are the main disadvantages.
Decentralized systems tend to be less scalable as we've observed.
Also, I don't think it's fair to compare Bitcoin with a payment system as bitcoin is not suited to be used for shopping, specially online shopping.
Is this a bad joke? Bitcoin is optimal for online shopping.
EG go to india and tell them its "low fee". and then give them just enough bitcoin for an hours labour and see it evaporate in the fees alone.
Nice relative privation.