It's hard to say without knowing you! It might be because they see in you very strong skill with old flaky code that others are not trusted to fix but it could

It's hard to say without knowing you! It might be because they see in you very strong skill with old flaky code that others are not trusted to fix but it could be that they see you as old-fashioned, uninterested or unmotivated and therefore they don't "feel" that you will be the right person for new stuff. You could always build some things and then talk to the bosses and ask them. If they can't give you an answer, it is likely to be a negative reason but if they can say e.g. "we didn't know that you knew this new stuff", you can show them what you have been working on.