I was subscribed for some time, first time as beginner and some years later as an intermediate.
There is a lot of content and some of it is very good. Very helpful - for me - were videos from Seymour Bernstein, Boris Berman and Boris Giltburg. Also from Magdalena Baczewska and Leann Osterkamp.
I think every piano student can benefit from Tonebase if you have time to regularly watch videos. Some of these videos are good structured und not long, but some are maybe too long for the containing content, especially from the Tonebase-own teachers. There is a lot of variety presented, it's like recordings of different masterclasses. And I think that is the main difference to other piano online resources - it's not a systematic approach, but a compilation of tips and tricks. There are many different teachers, who contradict each other. Bernstein and Berman and Penelope Roskell have their own vision and vocabulary and they are not easy compatible with each other. And there are also many Taubman videos with a completeley different approach. As a beginner I was paralyzed by all the choices and different opinions.
For a beginner there are better organized alternatives. For me the best overall technical school is Entrada from Bernsteins student Fred Karpoff. Piano Online Academy is also very great. I was subscribed for both of them and can recommend them more than Tonebase for your first years of piano playing.
For learning piano pieces the best videos for me were videos from Denis Zhdanov. Very systematical - from first bar to the last everything is explained in detail. Followed by Entrada. And of course Piano Online Academy - also very systematical and there is a lot of content there. I think more than on Tonebase. Especially for beginner-intermediate stuff.
What makes Tonebase unique is variety and some of the teachers are world class performers. But it's really more like visiting a masterclass, not having a teacher. These videos don't explain a piece from beginning to the end. The teachers pick some bars and sections, give their tips and share inspiration and love for the music.
And a lot of the pieces on Tonebase are advanced. Chopin Etudes and Ballades, Rachmaninov, Ravel and Liszt.
So I think for the advanced player Tonebase is the best, but maybe not for the intermediate student.