I guess my experience came from when I started playing many years ago and started trying out healing. My friends who got me into the game explained that there was proactive healing and reactive healing, and for doing dungeons and being proactive I had to learn which mobs and/or bosses needed proactive heals. I didn’t use any healing add ons, had no idea how to use them or set them up, nobody taught me and the only one for dungeons that I liked was Healium (yeah I know, a weird clicker add on but I used it and liked it and for the content I did it was fine).
Obviously you cant use it in raids and I never healed raids so that wasn’t really an issue for me. So my experience at such things is very limited.