still not clear what good ctr for google ads is

Depends a lot on the industry and on whether it's your brand name. Search ads on generic keywords landing somewhere in the low-to-mid single digits is common, while brand campaigns can easily sit at 20% or more because people are already looking for you. Compare against your own account rather than an industry average. If one ad group is way below the rest, the ads don't match what people searched. Display is a different world, well under 1% is normal there.