i stopped caring about the FBI and the CIA. we cant live our lives worrying about them. vpn or not, they can locate you if they want.
however, your ISP is allowed to sell your browsing history, and walking around getting unknown wi-fi signals can lead to a breach of your data from your phone. vpns can also stop you from getting advertisements targeting yourself (speaking a word while the cellphone is nearby will trigger an ad in that same vein). i suppose its less of a concern for home desktop or laptop people, but vpns allow you to circumvent government censorship (like when you go to youtube and you arent allowed to watch a music video because its banned in your country). so if youre in china, a vpn is essential.
heres a list of free ones i came across while doing a bit of research to answer your question. that proton one is recommended by the editors, for what its worth.
https://www.pcmag.com/roundup/285788/the-best-free-vpn-services