Why is my CTR dropping in Search Console?
Your CTR chart is sloping down and it looks like something is broken. Before you rewrite every title, work out whether anything actually got worse.
Check clicks first, not rate
CTR is a ratio, and a ratio falls when the denominator grows. If impressions grew faster than clicks, your rate falls while your traffic rises. That is what expansion looks like on a chart, and it is the single most common false alarm in Search Console.
Three causes that are not decline
Ranking for more queries at worse positions pulls the blended rate down. A seasonal shift in query mix does the same. So does a brand-query share that is growing more slowly than non-brand impressions, because brand queries click several times higher than anything else and dilution is not damage.
What a real problem looks like
Clicks flat or falling while impressions and positions hold steady. That is a snippet problem, and it is worth fixing. A CTR fall with rising clicks is not, and rewriting your titles in response is how people break pages that were working.
Check whether the drop is arithmetic before you treat it as a problem
Divide the period in two and look at clicks and impressions separately. If both rose and CTR fell, nothing broke: you picked up impressions on queries you rank badly for, which drags the average down while the business gets better. If clicks fell while impressions held, something in the result changed. Only the second case is worth a week of your time.
The three causes that are actually yours to fix
In order of how often they turn out to be the answer: the title is being rewritten by Google into something less clickable than what you wrote, a rich result above you is absorbing the click, or you drifted from position 6 to position 11 and the fall off that cliff is far steeper than the position change looks. Check them in that order, because the first is free to test.
Measured, not asserted
On this site the rate fell every month from March onward while clicks rose every single month. April: 4,409 clicks at 6.02%. July: 16,410 clicks at 2.72%. The rate more than halved, the clicks nearly quadrupled, and nothing had got worse.
Free tool for this: Search Console Analyzer. No account, nothing uploaded.
Where this goes deeper
Every number on this page comes from one complete dataset: one product taken from zero to 100K+ users on search alone, with nothing spent on advertising. The full argument is Chapter 16 of the book. Five chapters are free to read.