HTML and CSS are expressive, have a vast selection of libraries and tools, and can actually result in shippable code. Designers and front-end devs should learn and use it.

But I don't see the point in creating a design tool unless it's meaningfully simpler than HTML/CSS. I reach for Figma when I need to quickly mock up a dozen iterations using our design system and fancy rectangles. It's fast enough that I can make mockups in realtime during discussions with developers and subject matter experts. But if I'm actually going to take the time to set constraints to make things flex properly or make a real table then why not use HTML and CSS directly?