I think ‘the angels at play’ in the poem ‘I Believe’ by Brucellish K Sangma could also signify the people who have left a mark in the society like described in the 4th stanza. Is it open to interpretations or does it have the specified symbolism?
In literature, every single line of every single text is open to interpretations. You can always find meanings, if it makes sense to you.
And here, on this particular line, ‘watch angels at play’ typically refers to something unattainable, or at least, difficult to achieve. So, it may suggest achieving great heights of success in what one does. It may suggest reaching higher social position. ‘Angels’ literally refers to the spiritual beings who are beyond our reach. And yes, of course, it may signify the great, successful and virtuous people who have received the status of angels by their virtue and work.