The people who make a living reselling have my respect; I don't have your patience or willingness to deal with crazy. I think that more people are worried about money, so they are more inclined to sell their items rather than consign or donate them. Which is making the secondary markets a little crazy (seriously, on Posh
I saw an authentic vintage Judith Leiber Minaudière sell for $40, and another damaged one be posted for $5000)
I do fund new purchases by selling stuff in my closet.
1) I am crazy picky about what I buy these days; I buy primarily for myself. When I do sell on Poshmark and that ilk, it's things in my closet that I'm ready to move on from. I'm that person at the thrift who only buys the occasional hat or box of fountain pens.
2) I do pay more than usual thrift prices most of the time; sometimes I'm lucky but I didn't regret it because of:
3) In 2016-2018, I could go and sell a bag on facebook groups for what I paid (often $100-300)
4) In late 2018, nothing sold in my usual groups. So in late 2018-2019, I started selling on Posh. Last year, was fine - I sold about 50 items with no problems. Mostly jewelry, some bags. This last two months? It's been a disaster. I sold four bags on posh; one was returned because it was vintage and "the marks don't look like the marks on a newer bag."

(This is the bag I spent over $300 at Bottega Veneta to have it relined and restored) Another was returned because it was "stained!" which, again, I had a ridiculous number of bright light photos... Which taught me, not to accept offers and that 2020 is the year of buyer regret.
As for buying - in November and December of last year, i was able to pick up some Christmas ornaments crazy cheap. I also found few nice pieces of jewelry, and the duffle bag to round out my travel collection. This year, in the last two months - I've found one bag.