I think one big factor might be the community itself and especially the marketplace for plugins assets effects and such. People are generally lazy, and don't want to reinvent the wheel.
When I started using Construct 2, the forum section for those kind of things were the way to go. With the transition to C3 I noticed that there is still very few plugins ported. Many are unsupported, many broken links.
A lot of Non-Coders are heavily dependant on good plugins for making life easier, or just because some things cant be done out of the box, or can be done with poor performing or complex workarounds.
If I were Scirra, instead of trying to cater for all various needs and requestsfocus on the plugin developers. for example:
** Create an easy tool for non coders to build plugins, behaviours and effects, for sharing with the community.
** Make it easier and more profitable to share and monetize plugins... Not everyone want's to share their hard work for free.
** Add an in-app plugin marketplace. For ease of use. Just directly browse available plugins and assets from within Construct and click install/add/purchase.
** Better marketplace in general for everything from Assets, Plugins, Templates.
I think those are the main pain points for me at the moment. I wouldn't mind using my own money hiring devs to create and maintain plugins if Scirra made it easy for me to monetise them, and for people to find them.
So in short.
Steps for creating and sharing plugins and behaviours or even events/code for non coders is a hurdle, and even if you are good at it, it's hard to get exposure and hard to monetise your creations. Plugins are hidden away somewhere in a website section where you have to browse, search, download, install, restart construct, open again... Way way way too many steps as a user to find and use plugins... can't even imagine the hurdles of creating one.