With an open source project, it's unlikely that a person will appear and offer you anything and lead you down any alley. If you're trying to cross a river and come by a raft and start whining about the lack of a bridge, let alone saying that someone wasted your time, you're ungrateful.
"TODO: build bridge" means that the author thought that it's a good idea to build a bridge, however the author has other priorities and has postponed the bridge building to the time that it's actually needed (perhaps by someone else). Now you stumble by in need of a bridge, what should you do? Build the damn bridge, of course.
You're not owing any gratitude to anyone, but badmouthing someone for not doing exactly what you want is plain bad behavior.
There's a difference between finding a raft (here's some source on github which takes a few minutes to look at) and being enticed by a bridge (here's a homepage showing up in search results, presenting a packaged solution as an answer to the problem I'm having, which doesn't turn out to be a problem until hours or days of integration work).
"TODO: build bridge" means that the author thought that it's a good idea to build a bridge, however the author has other priorities and has postponed the bridge building to the time that it's actually needed (perhaps by someone else). Now you stumble by in need of a bridge, what should you do? Build the damn bridge, of course.
You're not owing any gratitude to anyone, but badmouthing someone for not doing exactly what you want is plain bad behavior.