Are engines destroying correspondence chess? General opinion says, 'yes', but what are the facts? One useful metric would be the percentage of drawn games in events at the highest level, the World Chess Championship : Correspondence Chess. Since engines are the great equalizer, at least tactically, you might expect the percentage of draws to be increasing.
The following graph, taken from A Database for ICCF Finals that I created a few weeks ago, confirms that trend. The stacked bars show the percentage of wins for White (yellow), wins for Black (red), and draws (blue), starting with the 1st WCCC in 1950, through the 24th, completed recently. The years correspond to the start of each event.
The latest event had more than 70% draws (101 out of 136 games) plus less than 10% wins for Black (12 games). If the trend continues, we'll eventually see some yellow, no red, and a lot of blue.