Thanks for bringing this.
I was actually waiting for the best opportunity to start discussing a very related topic, but from a maintenance POV not a user one, and I think this is a good one:
*What is the value and quality of SimRel? Is it worth it's cost?*
As you're highlighting, the actual SimRel doesn't result in good "common" toolset. Installing whole SimRel leads to a failing or non-usable IDE. So is this non-functional thing worth it?
EPP packages behave fine, they're tested and delivered to the target audience in a good enough shape. Marketplace is now the main and best entry-point for many features and fits much better into typical user workflows
Does SimRel bring anything really good beyond EPP packages? Anything good enough to be worth the maintenance effort?
Is it an interesting exercise to expect all Eclipse Platform plugins in the Eclipse Foundation to work properly together as the same application? Who is actually likely to invest in making their specific plugins fit better with all other Eclipse plugins if the typical audience doesn't care?
My opinion on this is that SimRel is nowadays a giant hard to maintain inconsistent effort, and that EPP and Marketplace have superseded it and made it not so profitable anymore.
I would suggest that we just abandon SimRel in favor of EPP building packages and a p2 repository containing all the dependencies for these packages; and other plugins should just target Marketplace as entry point, until they reach a good enough quality and value to get into some EPP package.