I feel like this can really vary by person. Some things may be more important to others.

I personally think seeking ways to improve transit and reduce car dependency is an important task. A lot of other commentors mention electric cars. These are conflicting goals but both solve similar problems and may be worthwhile to work on.

If you are interested in seeing what jobs are actually out there, I think "80,000 Hours" is a good place to start: https://80000hours.org/start-here/?int_campaign=2021-12--pri.... I don't think they are always perfect, but I think the idea is in the right place and their job board often has roles that are working on important problems for humanity.