A footnote gives a writer somewhere to place material that would interrupt a sentence or paragraph. It is less helpful when the reader must keep leaving the main text to understand the argument at all.
Try reading the piece with the notes temporarily covered. Can you follow its central claim and the qualifications necessary to interpret it? If a crucial limitation disappears, it probably needs a place in the main text.
Some notes identify sources. Others explain a term, acknowledge a complication, or offer an optional aside. Those functions can coexist, but a reader should not have to guess which kind of help a note provides.
For a draft, label each note by purpose in your working copy. Then look for two notes doing work that belongs together, or a long aside that could become its own paragraph.
Do not use small type as permission to include material that has no real role. Optional reading should still reward the person who chooses it.
After revision, test the route in both directions: the main text alone, then the main text with every note. Both should feel deliberate. The second route can be richer without making the first one misleading.