Ranked-choice reduces transparency and understanding of the vote-counting process, disenfranchises an alarming percentage of lower-income voters, obstructs risk-limiting audits (which are essential for security), and is non-monotonic (increasing voter support for a candidate can make them lose). Further, ranked-choice doesn't actually fix the spoiler problem and won't eliminate two-party dominance.
Approval voting is cheap and easy to implement, dead simple to explain, count, and audit. Not only does it eliminate the spoiler problem, it is easy to see why it does so: your ability to vote for any candidate is independent of your ability to vote for any other.
I know, it sucks. Politics is terrible. But we have some momentum behind RC/IRV so we should use it and stop the single-vote FPTP system that's plagued us for centuries. Anything is better than that. So let's join forces and get behind whatever has momentum even if it's not technically the best.
A ranked choice ballot at least requires you to assign a unique value to every candidate on the ballot: you can honestly rank your second choice without being concerned that doing so undermines your first.
That's highly implementation dependent. Where I live we have ranked-choice ballots for local primary elections, while the local general elections are FPTP. State and Federal elections are all FPTP for primary and general elections.
While I am free to rank up to five candidates when filling out my ballot, I am not required to use all five choices.
I can just ignore all that if I choose and just rank one candidate first and leave the rest of the ballot blank. Or I can rank multiple candidates, but I'm not required to "assign a unique value to every candidate on the ballot."
In fact, if there are more than five candidates for a particular office, I can only rank five of them.
All that said, I'm absolutely in favor of RCV and wish we had it for all elections, not just local primary elections.
Not so dead simple to vote, though. If you're a sincere voter and you prefer Alice to Bob and Bob to Charlie, do you approve of Alice, or both Alice and Bob?
That choice has to be either strategic or very noisy.
There seems to be some unavoidable complexity to voting methods: letting the voter deal with the complexity leads to a method with a very simple algorithm but that's tricky to use. Letting the method itself deal with it leads to more complex algorithms, but makes it easier to vote.
That said, the alternative vote is a bad ranked voting method; with that I do agree. Just beware of the complexity hidden in the system, whether that's Approval or Ranked Pairs.
My position admittedly breaks down when people lie to low-information voters about the fairness of the process - but, in my defence, people will lie about any system that doesn't produce the results they want. I'd prefer they lodge their objections to a better system than first-past-the-post.
Even by its nature, ranked choice means that radical ideas need to temper themselves or somehow be extremely popular. Trump never would have won in a ranked choice system.