Yes they are!
Yoona is the only one who was going to be successful no matter what happened because she was huge since before debut. Korea was always going to be in love with her which means SM was always going to give her what she wants.
I love how the rest play their cards first with SM and then after SM for those who left.
Those who want to do music in Korea and have stable variety show promotions definitely stayed with SM because SM has the power to promote them well. Yuri chose to do it all; music, acting, modeling, variety shows, cooking.
Hyoyeon is different, she knew that her solo music career wasn't going to be so successful so she chose to be a DJ, something that can enable her to make her own music and also tour in different clubs around Asia and she knew that SM would make it easy. Honestly, I think she gets to have the most fun because she parties and works at the same time.
For those who left, they are smart enough to know that a music career in Korea, without a huge Korean label is almost a waste of time so Tiffany went to the US for music and came back to Korea to tour, do a huge musical, model and act. Which is super smart, I mean, look at her now!
Meanwhile, Sooyoung and Seohyun know exactly what to do, they turn music and dancing into a hobby and become full-time models and actresses. That way, they can't be hindered by anything to do with music.
Everyone gets to do what they love while keeping it real and fun and still making bank.
Honestly, if all the other older groups had done something like this, I'm sure they'd all still be relevant too.