Yes, this has popped up before. To me the accessibility argument is far more important than the SEO one.
When you dump an image in a post and give it no description, blind people reading the forum are at a great disadvantage. They lose extremely important context.
AI can help bit here and provide automatic titles. I would say it performs okish, but has plenty of gaps.
As an opening move I recommend creating a theme component .
force users to provide titles on images
When enabled and you post anything and forget to enter a title for your images we could prompt you with a intermediary bootbox that reminds you to add titles to your images.