Hiring managers here, are there any signs you've learned to pick up on that indicate actual technical proficiency?
However, as a hiring manager you have to allow some slack for people to learn as they go. Otherwise you will never hire anyone.
In interview terms, that means I might ask "Tell me about the things you do to stay up to date in your field, and/or learn new technologies."
One answer might be "I read a few blog posts here and there."
Another might be "I take online classes via Coursera and Udemy, read books, read blogs, read papers on arXiv, and attend conferences."
All things being equal, I find that the second person usually winds up being the stronger developer over time. It's not a perfect correlation though.
On a related note, part of what I try to look for in interviews could generally be described as "enthusiasm". People who seem to genuinely like programming and working with tech, and find it inherently rewarding, tend to be the people I prefer to hire and work with.
As far as nitty gritty technical stuff, I usually like to ask one or two questions that I know that most people won't know the answer to. If a candidate doesn't know the answer, well, "no harm, no foul" as they say. But if they do, it's their opportunity to score some extra points with me. IOW, not knowing isn't a disqualifier, but knowing is a perk.
On those, I try for questions where you can't just memorize a stock answer, but rather need some conceptual understanding in order to answer the question. Usually I try to phrase it in terms of effects, or needing to understand some causal chain. In other words "If I do X, what will be the implications in terms of Y?"
* Do they have original work publicly available? (Github, Gitlab, ...)
* In the interview can they talk in more than surface detail about past work/projects.
* Do they have a blog where they talk about what they've learned over their career?
Hiring is always going to be a risk but looking for ways to see or get them talking about what they've built and what they learned while doing it is the most effective signal I've found as to whether they can do the job.