Segwit got activated 6 months ago and only 10% of users use it.
That's because segwit was badly implemented. There's no buttom on QT to create segwit addresses, you have to use a console command.
You cant expect the average user to be writing console commands, specially when most of them dont even have patience to synch the entire blockchain, and prefer smartphone wallets instead.
Also, segwit only gave me a 15% discount when I tested it. To send 100k satoshis, you still need to pay approximately 80k satoshis in fees, sending from a segwit address.
Core has been delaying proper segwit function at the GUI level because they don't want to push it into the system prematurely so they only let experienced users to access segwit functionality with the command lines.
With 0.16 it will be on the GUI and anyone will be able to use it as usual just like legacy addresses.
Coinbase has said that they are working on segwit and also on lightning network, check their twitter. So soon enough we will see a massive increase in segwit usage and late on on lightning transactions.
Concerns explained by OP will be taken care off eventually by making user friendly GUI's.
Ultimately, we will find out if it's a failure or not once it's working at scale. What is clear that will be a failure is the "blocks-as-big-as-needed" route (BCH)