It sounds like you’re good at working on those legacy systems and become more so as you keep working on them. As long as the legacy projects are there and need

It sounds like you’re good at working on those legacy systems and become more so as you keep working on them. As long as the legacy projects are there and need a maintainer, of course you’re going to be offered that opportunity. So then what happens? You get offered that role. What do you say? That’s the part you might need to work on. You might be giving an answer that is in more service to (say) your sense of duty than to your career ambitions and creative interests. Give some thought as to which is really your priority.