25yo legacy app
Hmmm.. Michael Feathers’ famous definition of Legacy Code: “Code without tests.”
Seriously, I mean to help.
So are you Scaling with ‘Scrum of Scrums’? Or something a little more structured like Nexus, LeSS or SAFe, etc.? (Or is it rather more like ‘The Wild West’?)
But why are the Teams under a lot of time pressure? They are meant to be able to maintain this pace indefinitely – are they very poor at estimation? Are they doing sufficient Backlog Refinement? Which technique do they use to estimate – Relative Sizing or Capacity Planning (i.e. Time)? Or is somebody else from outside just “pushing” the work onto them?
Why not take a look at Henrik Kniberg’s checklist and – be honest – count how many your aren’t ticking? https://www.crisp.se/wp-content/uploads/2012/05/Scrum-checklist.pdf
Scrum should be bringing Transparency through its Principles, Practises, Events and Artefacts:
Potentially Shippable Increment = Fully merged, fully tested.
Continuous Integration = Merge to trunk (i.e. no branching).
Definition of Done. (Basic one that all the Teams agree to, with more exacting and tighter definitions for the better Teams, once they have started the Continuous Improvement process).
Continuous Improvement of processes, tools and techniques.
Who is the Teams' Scrum Master? The phrase, “Where Scrum isn’t fully adopted and fully understood,” is used as a caveat to give Scrum Master’s a bit of elbow room to correct errant behavior… Maybe time to have a word with the SM?
25 years ago = circa 1992 code, and so I’m guessing primarily C/C++? (If not Pascal or COBOL or something?)
Now I’ve used .NET static-analysis tools before to help identify redundant, legacy code. (But I'm sure there’s C++ stuff out there - have you checked into this?)
Does sounds like you’re already aware of your problem – a lack of Technical Excellence and Discipline (probably brought about by a lack of Transparency) – what can you do to hold them to account? (Are they Pairing?) Maybe you could work on their Teams for a Sprint and check that each Story has a Code Review Task? Or how about Martin Fowler’s “StranglerVine”? (Pay down that Technical Debt?)