"Free Wi-Fi" also almost always means "no encryption on the PHY" meaning eavesdropping is trivial and MITM is much more likely. I never use public, open Wi-Fi without wireguarding home.
Do I trust ProtonVPN’s free tier less than I trust a random access point named (say) “NYC Free WIFI”? I would say no: I know who ProtonVPN is, and I’m only trusting them, not all their other users.
I agree a lot of free VPNs are shady as fuck, but free tiers from reputable companies are reasonable, and if anything may be more trustworthy than your home ISP.