Having used VisualEditor in non-WMF wikis, my experience was initially the same. Although that wiki didn't have as many extensions as Wikimedia wikis do. But you do get used to recognizing the icons, rather than the words in time.
The order of the tools should be reconsidered. For example, why is "Hieroglyphs" (something most users will never use) the fifth item, coming before tools that are used more often?
There is an order, it is just not obvious to some. The order of the menus is seemingly from most used items. At some point it seems that they just started appending to the list.
Could the order and selection of the tools depend on the user and the context?
It varies by wiki, mediawiki.org doesn't really cite a lot of stuff, so they just put the cite button into it. On wikipedias that icon is in the toolbar. Changing it by context is a really bad idea because it will just end up being confusing to users who expect the button to be somewhere but changes on some pages.
Would a hierarchical menu (once these are possible, which currently isn't the case) improve the usability?
This is one reasonable approach to grouping similar actions, whenever that is implemented.
Are there other users with better ideas how to improve the insert menu?
Until sub-menus are implemented, there are a few tricks they can use:
- Use separators (horizontal lines) between items to separate similar actions
- It should generally have 5-7 elements per usability guidelines with a scroll bar for more, A very long drop like that is pretty bad.
- Group similar actions separately from frequent ones with either separators or some other visual identifier.
- Maybe add a new widget that allows typing to filter the list, with appropriate aliases, e.g. video, photo, music -> media
- Add an extra toolbar that can be toggled (and hidden) like the insert character menu, and this would contain other more frequently used icons.
Generally, it might be a good idea to look at what other non-WMF wikis have done, maybe shoutwiki or other wiki farms. Wikia for example, somewhat redesigned their tool bar adding a second toolbar and moving the media button (images & video) along with the gallery to this new toolbar.