> Little pictograms for buttons are often extremely vague and open to interpretation.
True. I remember Lynda Weinman refered to this as "mystery meatball" navigation in one of the books she wrote on web design somewhere between the mid 90's to early 2000's. Probably it was the book Designing Web Graphics.3 [1] as looking through the Google results the cover of that one looks the most like what I seem to recall.
Tying into what was said in a sibling comment about the icons used in programs like Photoshop, I think the important thing to keep in mind is the context in which you consider adding icons. For a professional market piece of software like Photoshop where you expect your audience to put many hours into learning how to use the software and where you expect them to become power users, you can allow more in terms of UI elements that might steepen the learning curve, but which when learned can be employed by proficient users for faster and more productive workflow and which therefore will make the additional time required to understand them increase the value that your software provides.
Meanwhile for tools and websites that are used only occasionally, or where you don't expect repeat use but want to provide the best value for your users still, you should hold their hand more and make it immediately apperent what everything does and how to use it.
I've been thinking a bit about interfaces that would evolve with the user but my conclusion thus far has been that the amount of work required to implement that successfully would take a lot of time and might even never be worth it. That instead it still seems better to me to decide wether you are targeting heavy repeat use or not, and to optimize your UI accordingly in the manner I stated in the above paragraphs of text.
[1]: https://www.amazon.com/Designing-Web-Graphics-3-Lynda-Weinma...