Yes I use it, because it's a basic generator thats why.
Also 3x Osc is absolutely necessary for beginners and people who want to learn synthesis and generators. It wouldn't be practically to teach someone Sytrus without learning how basic oscillators work. Teaching someone Sytrus without learning the basics is like teaching advance algebra to a young child (who barely knows basic math, like adding and subtracting).
That is also the problem with the tutorials out there. Seamlessr is knowledgeable (yes!) but he's not a very good instructor and he's not great at explaining things thoroughly, he goes from 0 to 100 and so many steps are missed and I dont believe he realizes that and I dont believe he realizes many people have a hard time following and keeping up with his instructional material.
Also, let me tell you a story about an instructor and a student learning FL Studio and the 3sOsc. So once upon a time there was a knowledgeable instructor who mastered FL Studio and a student (who wanted to learn FL studio) who was eager to become better and learn sound design. The instructor started teaching the student about synthesis and oscillators and started the curriculum with 3xOsc. The teacher sent the student home with homework and the homework centered around 3x Osc and layering sounds. The student went home and completed the homework and started going the extra mile by experimenting further with 3x Osc and started layering and creating their own sounds. The student then further experimented more by loading up Patcher and tried to load 3x Osc within Patcher, however the student couldn't load 3x Osc into Patcher and couldn't figure out why. Long story short the student got frustrated and quit the lesson and quit the school and quit FL studio and the student started to try new programs and take new classes (masterclass) from other instructors and the story ended up sadly ever after.