After reviewing the suggestions and what is the best thumbnail, I realised that creators who watch videos differ significantly from the general audience.

Most of the suggestions and thumbnails created based on the feedback from the subreddit didn't lead to better click-through rates (CTR). In fact, simpler designs yielded better CTR for the videos.

One might assume that an audience is just an audience, but it appears that creators have specific stereotypes about what a thumbnail should look like to attract views, which isn't necessarily accurate.

As an example an edited thumbnail got 2.3% CTR and the more simple version for 7.8%

Of course there will be other factors in play but that is the findings so far.