It's perfectly OK to blame the agile manifesto. Part of the issue with the agile manifesto is it was written by developers, which makes it sound credible. In addition, you have a lot of cult adoption by developers, which made it difficult to refute. Once law is written in stone and some boundaries are established, that's when business processes come in and do what they do best: see how to manipulate their actions around that language to get what they desire from what is accepted/legal. They tend to always find paths around the bounds that lead to new undesired behaviors.
I used to run public community driven online video game servers in a different era and they were quite popular, sometimes the most active/hearts in their communities. One thing I always struggled with was writing down rules for player behavior on the servers. Once I write a rule it does two things: establishes what NOT to do explicitly, but opens a huge gray area of what isn't explicitly defined that can be done or opens up a subjective gray area that shouldn't be done but is not clearly defined. I now have to enumerate everything I don't want people to do which may be a massive list if you want clarity and no ambiguity. People get creative, always, and find new undesirable behaviors within your rule framework.
In the end, when you write some base rules, the only real solution is to continually ammend the bounds of your rule system over time to adapt and adapt, leaving less surface area to attack. This is why the US legal system is so darn complex. Basic constitional laws are established, some explicit don'ts, some explicit dos, and everything missing becomes questionable. I didn't want to do this on a video game server because... it's a video game server, nor did I have the time. I instead took the "it's private property and I am the tyrrant approach" and wrote a very simple rule to play with etiquette, then ruled over the server benevolently (at least I think so, joining anonymously for occasional sampling to adjust some server settings I found being abused and never banning people just because they were unenjoyable to play with) and it worked well. The servers remained the most popular servers.
The agile manifesto never adapted and business leadership is who calls the shots. A culture said let's adopt this and businesses said ok, sure, then this is how we're going to interpret these poorly defined bounds. You said this is what you wanted and everyone agrees so here you go. For the US constitution, vagueness and broadness works well because it was designed to be a living, extendable, changeable document. The agile manifesto is not. Given how well businesses skirt around the meaning of law to do legally, ethically, and morally questionable practices, what hope does some silly manifesto with no teeth someone writes have? Business rule as small little hierarchical dictatorships with tyrants ontop within a democracy and I've found the characteristics that compose leadership is often the opposite of benevolence. Be careful what you ask for in such environments, your requests will be twisted against you.