Having spent an unhealthy amount of time thinking about this, I think it's even worse than an abstraction _level_.
I suspect that the fundamental problem with visual languages is that you have to reify _something_ as the objects/symbols of the language. The most widely used text languages tend to be multi-paradigm languages which have significant flexibility in developing and integrating new abstractions over the lifetime of projects and library ecosystems.
It's not clear to me how this can be overcome in visual languages without losing the advantages, and instead ending up with a text language that is just more spread out.
I think the solution is just to stop trying to allow Real Programming in visual languages.
Make the abstractions purely high level, and let people write Python plugins for new blocks with an app store to share them.
Visual can easily provide enough flexibility for gluing blocks together.
IFTT, Excel, and lots of others do it perfectly well.
The issue is programmers like to program. Mostly they like "programming in circles", making little apps to help make more other little apps to explore ideas.
They see it mathematically, as a human centered activity all about understanding, while users see machines as a box you put stuff in to make it not your problem anymore.
They're always talking about empowering users to create their own fully custom ways of using computers... But.... I like apps that have a canned, consistent workflow that I don't have to fuss with or maintain or reinstall.
Software like Excel has the appropriate amount of power for working on a project that uses computers but isn't really related to programming or done by developers.
I suspect that the fundamental problem with visual languages is that you have to reify _something_ as the objects/symbols of the language. The most widely used text languages tend to be multi-paradigm languages which have significant flexibility in developing and integrating new abstractions over the lifetime of projects and library ecosystems.
It's not clear to me how this can be overcome in visual languages without losing the advantages, and instead ending up with a text language that is just more spread out.