The cause of complexity is not emotional attachment, these are decisions being made. The decision to add feature after feature and punt on maintenance for example is something that has little to do with emotions. There is a lot of agency that engineers, SWE and SRE alike have in shaping how things are. However there can be good reasons to abandon simplicity. The real trouble here is not psychology but that as a profession we are really bad at measuring and estimating the effective cost of maintenance. Part of that is considering measures to improve simplicity and maintainability as cost that comes without gain and somehow less important than features, and then just accept giant rewrite a few years later. A continuous portion of upkeep would likely be more economical and real engineering has always included an aspect of economy - cost vs benefit.
IMHO the loaded accusation of emotional attachment might be rooted in an "us vs them" attitude (SRE vs software engineering) that should have no place in a sober discussion on the value of simplicity and it diminishes an otherwise great text.