There're many amateur astronomers out there who build their own telescopes, write their own data-gathering programs, and scan the night sky tirelessly. Sometimes they even happen upon new discoveries simply because they had their telescopes pointed in the right direction at the right time.
However, the telescopes used by professional astronomers get more and more sophisticated all the time. This means that the window for amateur astronomers to contribute gets smaller and smaller all the time. For example, the recently-discovered Comet Borisov was discovered by an amateur, but the number of comets discovered by amateurs has been constantly decreasing. Which is obviously rather depressing. One day someone might write a poignant documentary which goes "I thought I was contributing, but then the professionals built [this telescope] and I've become redundant ..."
These citizen astronomers are obviously great PR for astronomy, but given the above, how can professional astronomers keep them engaged?