Architectural complexity[1]! There’s several really good papers on this.
Unfortunately it never caught on and we don’t have great automated tools to spit out a number. Also the majority of people just don’t care enough. Research in this field kinda died out when we invented microservices and started treating those as a silver bullet to The Architecture Problem (it’s not [2])
[1] https://swizec.com/blog/why-taming-architectural-complexity-...