Pretty sure that exact feature is built into the native Hue app, as long as you have the bulbs that support those kinds of colors. I see it when i try to make a “wake up” automation, i’d have to look again to see if there is an opposite for sunset. You can automate bedtime or go to sleep automations, and schedule them for sunset/sunrise or specific times.
Edit- just quickly looked through the app- there IS a sunrise for a wakeup automation, but not seeing any default sunset types. Might have to create your own by fading through some other sunset colors while dimming. Which is done basically like you are sayin; pick a color and and start time, then another color at another start time, etc. you can set whether to snap to these colors or fade to them over a period of time which also picking brightness. BUT- this is just in the native Hue app, i dont know about other Hue compatible apps.