The recently imposed upload size limits are too small in terms of resolution.
We use Realtimeboard for mapping screen flows - it allows us to annotate directly, illustrate flows between screens and components and have a single source of truth for the design, content and interaction of our features.
It is important that the images (typically screenshots) are readable and clear, and it would be quite an overhead to have to resize every image to meet your new limits.
I would suggest that you relax the limits on resolution, as a PNG screenshot could be well under 1Mb in size, but over 4000px in length. Similarly, experience maps produced in vector software can output images that are 10,000px wide but still only around 1Mb in size.
This does not seem like a change that has been made considering all of your users' needs and I would urge you to reconsider and iterate. Perhaps have a default resize function; as on WhatsApp the user has the option to send the full size image if they choose, but the default is a reduced size.