It all depends on team size and structure and the resources you can tap into.

A modular approach (microservices, faas, components, or designers who don't code but design many components in advance) can work better if there's a bottleneck regarding designers who can code, or regarding the constant communication between designers and coders.

Same is true if you have these resources, have coders who can design or vice versa, and can switch between design and development as you want.

That's important to understand, because most discussions about the best approach to design and development are actually about different environments, team structures and a different mix of skillsets.

Full stack designers or developers are more common and valuable in smaller teams, while specialists are more valuable in larger ones.

Comparing both approaches (holistic vs. modular) doesn't make sense without a context.

The current design scene (Dribble etc.) is very focused on modularity because that's what the big players, the Goliaths want. Basecamp and the hard core Ruby community (Basecamps founder created Rails) is more the David in David vs. Goliath. It's also part of their brand.