This question seems to come up 2 or 3 times a year.

Flight instructing seems most equivalent to graduate school teaching:
neither pay well, and neither are meant to be long-term careers.

They may seem unfair. But just as graduate school may be a really fun
place to be, being a permanent student is not something society seems
to want, so we won't pay for it to be permanent. Likewise society
seems to have decided that teaching flying in 30-year old, $20,000
airplanes isn't something that should support a family for the long
run.

I've found just about any job gets boring after several years...so
while I won't suggest you accept a well-paid, boring day job and
instruct on the side, it might be better than the alternative...a
boring flying instructor job (after a few years) that pays lousy.