For the bolded to happen the overall design would need to be a whole lot more modular than it is.
Modular design is antithetical to unified design, and unified design has (other than a brief glimmer of hope during 5e playtest) been a stated intent of every WotC edition.
		
		
	 
This isn't true. You can have unified design, and also have modular design.
Like...modularity can be actually significantly 
enhanced by having a clear, clean, unified core with consistent interactions/linkages. Having a consistent fundamental system makes it 
easier to add on local exceptions that don't jump outside their lane unless you allow it to.
For example: having both saving-throw-based actions and attack-roll-based actions results in dramatically more difficult design if you want to make a "tactical combat module" supporting 4e-style play, siloed off from the rest of the rules; both internally, because it has more things to interface with, and externally, because there are more interactions you have to test to make sure nothing goes wrong mechanically (e.g. the value of +1 attack is 
not the same as the value of a -1 penalty to saving throws enemies roll). If, instead, all offense actions are attack rolls, you can have various different approaches.
Or consider Dark Sun, with its hazardous environments and metal rarity. 2e's rather hodgepodge saving throw structure makes that significantly harder to design, and makes providing equally-well-tested alternative approaches difficult. WotC-era D&D with its standardized saves makes this much easier to test and implement, and allows you to 
see, directly, how it impacts things. Likewise, having a unified structure for how item design works means that you can make clear, straightforward rules for weapon breakage, more easily test to make sure that those rules are reasonable instead of extreme (whether ineffectual or excessive), and generally puts item-related stuff into an easier-to-handle space, especially since you can add setting- or context-specific properties or effects.
Sprawling, 
ad hoc, messy design usually doesn't make modularity 
easier. It just means everyone--designer or player--has a harder time seeing what the consequences will be, and a harder time testing for interactions. That will slow down players discovering unexpected synergies or poor-performing options...for the same reason that it will slow down 
designers discovering those things.
The only way it is "easier" is that you can go more confidently into wrong choices because you have less information.