Bizarrely, I've never seen Baby Ariel out and about in any of my 3 currently played saves, not even a previous save where I played through to Global Superstar with one sim. She's there in my unplayed households, but just doesn't seem to spawn. Since I didn't know who she was before she entered the game, I'm not really worried about it.
As for the Sims 4 'leaving older, loyal players in the dust'.... I'm an old, loyal player and I thoroughly understand the use of young celebs to bring a new generation of players into the game. I came to The Sims 4 by way of The Sims, The Sims 2 and The Sims 3 so by the time #4 came out I was already a loyal fan... younger people today are starting with The Sims 4 and have completely different expectations when it comes to gaming and media than my generation did as teens. I was busy playing on my Spectrum and then my first PC back then :D