I have seen strong evidence that the use of primitives is a major cause of slow loading times, particularly on Rpis. I was glad to see that was the first suggestion on the thread.
This also adds good evidence to that being the culprit.
It would really be helpful if you filled an issue on the ESH repo referring to this thread. I think this thread is the suggest evidence so far that primitives are the problem.
I can probably guess what you mean by the ESH repo, but I don’t want to make a mistake. Since you obviously know what and where it exactly is, please give me the link to the issues section where I may open up an issue.
While I fear this one is not the only one lurking it’s at least a starting point that can be used for further analysis.
I opened https://github.com/openhab/openhab-core/issues/451 and hope some knowledgeable core developer is willing to take on it.