Things don’t work like they did 10 years ago where you are constantly changing up things & making fast moves. If the campaign is converting well & the leads you receive are actually good then you might be thinking the wrong way. Now days, less is more with Google ads as they are more strategic than ever. It’s 70% analysis & planning, 30% execution.
But yes if the conversion rate is below average & leads are way more expensive then you should question his performance. But it’s been 3 weeks only so give him some time