There are a few different ways to get what you want, some of which have already been mentioned.
If it were me, and assuming I really liked the frame and am willing to invest to make it work, I would do either of the following:
1. New groupset altogether - look for used 10 speed - with a 34x32 climbing gear. It's a big investment but it'll make the bike slightly more modern.
1.b. Ok if I'm on a budget, then go with what others said, which is to get a 50/34 crankset (with BB if needed), a 32t cassette, and a longer cage rear derailleur to accommodate the 32t cassette. You will also need a new chain. Everything should come to under $200 from the used and AliExpress market.
2. New groupset altogether but make it a 1x flatbar bike. You'll need new stem and bar, rear shifter, rear derailleur, and cassette (and new chain). You can keep the current crank and use the existing middle ring. You save the crank cost but spend on a new shifter. Should also come out to under $200 if sourcing parts from AliExpress.