Synthesia just isn't very good, IMO. It lacks information, takes up a ton of space, makes it hard to read rhythm and patterns, mostly lacks fingering information, requires rewinding every time you want to retry a section, and so much more. As a notation format, I don't think it's all that good.

My Debussy book has no fingering (as Debussy intended), is that bad? My Henle Beethoven sonata book lacks any dynamics markings for Op. 49/2 and similarly for Henle's Mozart K545 Mozart Facile sonata.

On the other hand, my Schirmers' edition has an awful lot of dynamics and articulation and pedaling that just doesn't exist. It has bad fingering suggestions a huge percentage of the time.

Having too much info is worse than having too little because incorrect notation makes you play it wrong, while too little forces the student to do it themselves. For instance, writing in the fingers, figure out the performance/style of the composition, take creative liberties in phrasing, voicing, rubato, pedaling etc. instead of relying on one editor's opinion of how it should be performed.

With Synthesia, you're pretty much limited to what's on Youtube.

With sheet music, you're pretty much limited to what's written down. I see a ton of Synthesia videos where there are no sheet music for (not even for sell). How doyou propose to learn these songs without having the skill to transcribe it?

Not only that, but Synthesia nowadays exist for most stuff, Czerny etudes, Burgmueller etudes, Bach inventions/sinfonias, Mozart sonatas, Clementi/Kuhlau sonatinas etc. And it goes into the intermediate pieces (Beethoven sonatas, Chopin nocturnes/polonaises) and even advanced pieces (Chopin/Liszt etudes, ballades, sonatas).

I am actually curious, what common pedagogical learning pieces are you saying doesn't exist in Synthesia form?

So when people want to learn with it, they jump straight into pieces way above their level, like Für Elise or even Clair de Lune.

That's not purely Synthesia's fault. I see people doing this all the time even with sheet music. A few days ago, someone was complaining about doing Fur Elise with a teacher with no prior background and only been playing piano for a week.

I am not saying Synthesia is better, which it obviously/clearly isn't. But people here are so biased against it that they create that applies to sheet music just the same.