So now you need to factor in research time. Then, continual research time, every time a new library or version of a library comes out. And if your research turns up that, no, in fact, version X or new lib Y is not substantively better (by whatever metric you're looking at), do you count that research time as 'wasted'?
> how do you know you're not wasting time and effort?
You look at the results of what you're doing vs what expectations were, firstly. You can then, periodically, look at your efforts, and compare reports from others who are claiming to do the same thing, and ... occasionally... spend time determining if a different approach offers radically better returns on the effort/results you have now. Switching to XYZ may also involve huge amounts of refactoring, upgrade, migration, etc. How do you know all that effort won't be "wasted" if new platform XYZ is abandoned 18 months from now?
"efficiently" doesn't necessarily mean "at maximum efficiency". Also, "business value" is almost always intertwined with hitting particular date/time goals, which often trump technical metrics.
That's different than if I don't know that Sequel exists and I blindly use ActiveRecord. They're both ORMs. They can both read and write data from a database. And guess what — ActiveRecord is better for the vast majority of situations and everyone in the Rails community knows it, so my research into Sequel would have been time wasted.
Rails helps you avoid wasting time on this kind of stuff and pre-packages stuff that most everyone needs and where the alternatives are not substantively different.