One overlooked benefit of these frameworks is that they encourage people code in a certain way, which makes other people's life easier when maintaining it.
If the framework rules and conventions have been followed, everybody knows what to expect and where to find stuff.
Of course, some of these frameworks are short lived or change too fast, but the effect is still there.
They're far from coding standards, but can help in the same way.
Good point, and a big driver for other non-frontend frameworks such as Spring, Spark or Docker - everyone knows where to look and understands the shape of the source.
I also think that these 'opinionated' approaches encourage good practice (apart from EJBs - there has to be one black sheep in the family), embodying well thought-out design patterns and providing examples of problems they address.
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