In ~25 years or so of dealing with large, existing codebases, I've seen time and time again that there's a ton of business value and domain knowledge locked up inside all of that "messy" code. Weird edge cases that weren't well covered in the design, defensive checks and data validations, bolted-on extensions and integrations, etc., etc.
"Just rewrite it" is usually -- not always, but _usually_ -- a sure path to a long, painful migration that usually ends up not quite reproducing the old features/capabilities and adding new bugs and edge cases along the way.
"Just rewrite it" is usually -- not always, but _usually_ -- a sure path to a long, painful migration that usually ends up not quite reproducing the old features/capabilities and adding new bugs and edge cases along the way.