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?

No system can be flawless and bitcoin is no exception! So the fees and waiting time are real challenges at this moment. And the fees is expected to go up in case the price goes up further. So we have something called lightening network. Which is a side chain transaction Facilitator and where you can send bitcoins using low fees and the transactions are usually instant.
I think, people should start using LN more and more now because of these challenges! Otherwise, you will have to constantly look at the mempool volume and time your transaction for the optimum period.
The LN might be a solution, but it's been years and the adoption is still very low, so I'm not feeling optimistic about it. And while it's true that no system is flawless, I feel a bit sad about IOTA with the DAG technology not gaining enough attention and popularity. AFAIK, DAG solves the scalability issue which Blockchain cannot solve. With Blockchain, more transactions means more problems, whereas with DAG it's the other way around. But there are big problems with DAG at the beginning, especially with it being almost impossible to properly confirm transactions in a decentralized way. However, it could be a long-term solution (or a part of it). As for Bitcoin, it could be used for bigger transactions or when there's low traffic and thus reasonable fees.