I am still stuck to using Opera 58 because the new look of the browser is completely inaccessible to me. Trying to use the newest Opera 67 gives me eye strain within 5 - 10 minutes of using it (even when I use dark mode). One of the biggest reasons for this eye strain is this difference:
(Opera 58 above, Opera 67 bellow)
The new look with no borders and higher contrast make it so much harder for me to look at. I have the same problems with mobile.
The thing is, while these kinds of changes make Opera unusable for me, they can be much more preferable for other people, which is why I wish Opera made it's appearance more customizable (for example, give us options to adjust the contrast, brightness, and possibly colours) so that it would be more accessible by many different types of people.