anyone making decent money with tool or utility websites using display ads

Yes, utility sites can still make decent money with display ads, but RPM really depends on traffic source and intent. AdSense is usually the baseline, but many people test Ezoic or Mediavine once traffic is stable. In my experience, direct search traffic performs much better than social or random traffic for this type of site.

yeah you can try adsense and also a few other ad networks then compare rpm and traffic quality to see what works best for your site.

Yeah it may be worth checking a few networks alongside adsense and compare the rpm and for the tool sites or traffic quality makes a big difference.