Speaking as a programmer myself with over forty years of experience, and an advanced lilypond users, I can categorically assert that lilypond is not trying to be 'clever'. This is an utter misunderstanding. Lilypond is however trying to engrave music to the highest possible standard, and this is an immensely difficult programming proposition, hence the complexity under the hood, and the slight difficulties in the syntax. It's not meant to be simplistic or easy like ABC.
Music notation itself is a complex abstraction refined over hundreds of years. It does not 'leak'.
If you are not happy with the system, and it seems it does mot match your expectations of what a domain specific language should be like for music, it may be that you simply need to add ornaments such as cut to ABC, given that the safe mode in lilypond won't allow you to achieve what you want in a web app.
To give you a bit of context, David Kastrup is one of the principal ongoing developers of lilypond and few people have the in depth knowledge of the internals that he does. He is well aware of the various infelicities we have, but they are generally being worked on continously. As for lilypond breaking, I do massively complex New Complexity scores with many code extensions I wrote in Scheme, and I hammer the software all day long, and I can't break it, even when stretched to the limits. A testimony to the fundamental good underlying design and architecture. Most others have the same experience.
As a final remark, I have learned ABC over the last two days in order to help you out. It seems to me that it is better suited to Irish music tune notation, having just enough expressivity to set thousands of tunes. Lilypond is capable of it, but it is a big machine, and probably like killing a mosquito with a B 52 bomber. Given the near universal adoption of ABC by Irish players, I'm surprised nobody has created the Larsen ornaments for ABC - but then, notating precise ornaments in that music is probably more for academic analysis and comparison purposes than for session playing.