I use Cloudflare Registrar a lot and, very early on, was quite active on this forum, drawing attention to errors and giving feedback on workflow problems (I stopped because one of the volunteer moderators kept derailing my threads, so, it became pointless).
Now, I just want to note how much Cloudflare Registrar has improved. A huge turning point for me was when the API limits, that stopped many domains from appearing on the potential transfers list, were removed. Previously, users with over 200 domains had to either divide them into different Cloudflare accounts or just give up on being able to use Cloudflare Registrar. Removing that limit made a HUGE difference to me.
When I logged in today, I was delighted to see that a design flaw I posted about in November has been fixed. Previously, domains eligible for transfer were pre-selected with no option to mass-deselect, meaning you had to manually remove hundreds to transfer even just one domain. I asked for this to be changed to checkboxes that could be mass-selected or deselected with one click. When I logged in today, voilà, checkboxes!
I am grateful that the Registrar team kept working to improve the design. There have been a ton of other improvements and, now, with this most recent change, it is as easy to transfer domains to Cloudflare as any other registrar.
So, thanks to @SamRhea and the rest of the Registrar team.