Starting on April 6th, 2023, the “Overlay ads” ad format will no longer appear on YouTube to help improve the viewer experience and shift engagement to higher performing ad formats on desktop and mobile devices. Overlay ads are a legacy ad format that only served on desktop and are disruptive for viewers. We expect to see limited impact for most creators as engagement shifts to other ad formats.
source (YouTube Help Community manager's post):
Optimizing ad formats - overlay ads are going away in April [support.google.com]
in my experience, mid-roll ads are far more disruptive than overlays, but that's a sample of one.
expect to see more (pre/mid/post)-roll ads...