[FLUX-YOU]

Some of these solutions have code from 15-20 years ago. After the original authors left the company with deep knowledge, a complete UI redesign went from uphill battle to sheer cliff climb. Once every generation comes and goes, rewrites just get more complex. Even then, the code then was probably based on standards from that long ago, and its quality will most definitely slow you down. Now couple that with the problem of high turn over, and no one wants to handle the shit pile. We keep shoveling things over to get paid.

Considering the staggering size some of these projects are (peripheral evidence of complexity like table counts as mentioned here, and more solid evidence like raw lines of code, number of UI controls from big to small), it quickly becomes economically infeasible to put a modern shine on things when you have features you could be building to make more sales.

A decent UI in 2000 looked much different from now anyway. Also, the programmers probably aren't in charge of looks/design.