It's something most piano teachers advise AGAINST.
But I am of the opinion that anything that makes you play the instrument works.
Proper technique is also important so that playing is actually fun and not painful. Even just a few lessons on how to properly sit, how to avoid tension in your hands and so on can go a long way. There are video lessons that explain that stuff as well but you need to be very disciplined and really repeat these lessons over and over.
You can absolutely self-learn the piano. People that genuinely don't have the money for a teacher shouldn't let that stop them but it absolutely is harder. Set yourself up for success if you can.
I take weekly music lessons and have been doing that for a decade. After every lesson -- since the very first one -- I am amazed by how many simple things that I get wrong, and how many different areas where I could improve. The teacher just sees/hears that immediately, when you have no idea what you did wrong. And the music just sounds different.
Not only that, the teacher discusses the piece with you, tells you the efficient way to practice (a specific piece or specific passage) etc.
You would probably sound ok to a random stranger, but you quickly hit a bottleneck. You spend a lot of time doing incorrect/inefficient things without knowing it.
$100/hr is expensive, but well worth it.
The other problem is that their learning technique, in which you start with fewer notes and add in all the notes over time, is not good at ALL. It masks certain things from you and even makes some things harder at lower difficulties when it's playing some scale and you don't know that so you're just playing random notes in it. Knowing that it was just a pentatonic scale or something would make it much simpler. Instead, you're taught to just play isolated notes instead of learning how to understand what that scale was, how to play it, and how to apply that to other songs. It's almost outright hostile towards a big picture music theory based approach on teaching how to play and instead focuses on memorizing the specific notes for each section of each song.
Anyway, piano scales and chords are not challenging to learn compared to most piano technique. If you don't have a teacher then buy Hanon, get a decent music theory book, and look up Youtube videos. Any of these training wheels based learning approaches seem to just assume that once you do it enough you'll pick up the theory. No. If you can't afford lessons (which I stress are very important) then you should at least make use of simple music theory books and videos on Youtube.
Scales have specific fingerings and hand movements, including thumb over/under movements at specific locations.
They're not optional extras. They're essential for fluid playing.
More subtly there's also basic finger/hand positioning, which has to be a difficult combination of as-relaxed-as-possible but also firm and precise, so you get fine control over dynamics and timing.
If you don't learn the vocabulary of physical movements, you won't have the physical foundation you need to play notated music properly beyond the very basics.
At the moment, I’m focussing on working on my timing by playing rhythm instead of lead guitar.
If you haven't already, please PLEASE choose the "invert" option for the string order. Your low pitched E string (the red one) should be on the bottom of the strings. It will mean that all your work will transfer immediately to both guitar tabs as well as conventional chord charts. The fact that Rocksmith is teaching people to train their muscle memory on upside down chord charts is so insane to me.
Elton John studied at the Royal Academy of Music. Alicia Keys is classically trained. Lady Gaga had lessons from the age of 4.
Even someone like Vangelis - nominally self-taught, and not a reader or writer - had lessons when he was starting out.