Looking at all the features that older phones uses to have compared to newer ones, I never hear anyone talk about the removal of the notification LED. I personally really liked that feature, being able to see if I got an email, a text or missed a call without turning on my phone was awesome. My Samsung note 8 had this feature, but to my knowledge, newer phones (in the major companies anyway) have abandoned this feature. Did everyone else unanimously agree they don't care for this feature?
I didn't realize the LED was no longer ubiquitous! I rely on mine, and I take it a step further with missed notification reminder for a repeating audio tone every few minutes. I don't like having to stare at my phone all day long looking for work messages.
The major companies stopped doing it. Samsung, Google, not sure if Apple ever had one. But it seems like there are some companies still using LEDs, which is awesome. I really miss the feature.
I actually really don't like this feature, but I just went and checked on my S21, as well as my work S20, and both of them have a Flash notification option, which flashes the camera LED when a notification goes off. Is that what you're talking about?
I think OP means a designated RGB-LED on the display side which flashes in user specified color when you have unread messages. My Sony Xperia active used to have one and I am missing that feature too.