Legacy codes can be messy and complex since the skill of programmers who were involved in the software development was not necessary the same and many programmers have repaired the bugs and changed codes many times.
To make matters worse, if the software is very large and codes are connected complicatedly, it's too hard to replace codes written by old language or framework with new ones. Just extracting codes and rewriting them don't work out.
The app she explained seems to help programmers understand legacy codes.
She showed outcomes the service produced. Yes, the results seemed good.
However, some questions linger on. (Sorry if these have been already explained.)
Can AI read and understand the whole codes of the large software?
Can the service be still helpful even if AI can't understand whole codes?
Can't AI rewrite codes automatically?
(Of course, these things are difficult for humans as well. Thus the modernization of legacy codes is a very tough task.)

If these limitations are overcome, the service will experience breakthrough.