If you have healed in Classic, you are not really a “new” player, and should be able to take on healing in Retail.
I am no expert, since I don’t heal, but from reading what healers say, I gather that M+ dungeons are where the stress comes in, where there are A LOT of gimmicks in the fight that healers need to be able to cover, and they are run on a timer, and healers are often expected to contribute to DPS as well, especially at higher levels.
So a lot depends on where you expect to spend your time, raids or M+, and what level you expect to play at. Playing in low M+ and normal raiding is different from running M+ 15s all the time and HC raiding, and that is very different from pushing high keys and Mythic raiding.
So if you are not pushing for the 1% levels, it may not be as bad as you fear.
A key point will be to get in with a guild so that your runs will be stressless. Guilds will welcome regular reliable healers.
So I would say that if healing is what you enjoy, there is a path to it in Retail. It will largely depend on finding a solid group, though.
I HIGHLY recommend the Community Scared of Dungeons, a lovely group of people on Alliance, who regularly run M+. Join Community and the code is OeBkVKTLZ2