As someone who started using plaintext emails recently, HTML emails are still awful in 2024. Besides being a ugly hack on top of an originally text-only protocol, it encourages bad practices like top-posting, bad alignment etc. What's really intolerable though, is the external and dynamic content in email. I expect email to be a long-term record, not something that changes after I receive it. They should find another tool for that. Besides, most GUI clients just block external content due to security risks anyway.