From what I've read, Bitcoin now charges high transaction fee and long transaction wait time so it can't presently be used:
a) for a conversion from Bitcoin to cash?
or b) purchases using Bitcoin?

I think its only temporary because of the Network congestion and if the Lightning Network will be widely implemented those slow transaction will be the only thing in the past, But for now that it is not yet widely implemented we can expect more slow transactions and higher transaction fees that directly affecting most of Bitcoin users so for small scale users the fees are high enough and impractical but for the whales its not a problem.