While I agree with this I feel as though the Marketplace promotes competition between developers and not an open sharing nature such as Epic with UE4 being open source. There is nothing stopping the community from getting together to help Epic to provide better framework support and infact if there is any one group that has a wide range of requirements which could be used to develop light weight modular frameworks its the UE4 community.
I get where the OP is coming from and I start from scratch alot of the time because Epics templates are not really fleshed out enough for me to bother, I end up replacing most of their functionality and in regards to the marketplace content there are some nice packs but some are similar in that they arnt very fleshed out or modular.
Anyways to get onto the topic of the engine being barebones, I feel as though that partly has to do with the lack of modularity in core systems such as they Asset Editors, it makes it difficult for people to expand on the editor in particular and most of what we see in plugins is small bits of additional functionality rather than something substantial which goes deep into the engine.
Personally I feel as though the community could have the biggest impact and that if we could work together we could alleviate alot of these issues ourselves by pooling time and reducing wheel reinvention not just for us but also at Epic on the engine freeing people up to work on more substantial engine/framework systems 