I would have dearly loved one of these apps when I was first starting out many years ago, when even digital tuners weren’t available and you had to rely on pitch pipes or a trusty harmonica to tune to. Having waited all this time though, I find that after years of working it all out myself by trial and error, even having to decipher sheet music, I don’t really need such help.
I know it sounds rather smug to say so, but I’m sure you become a much better musician as you develop a good ear for keys/pitch, tempo, chord progressions and a basic knowledge of music notation. If I can do it then I’m sure anyone can, if they just take the time and experiment, and the more you do it the easier it becomes.
However, that’s not as time consuming as it sounds, because the process of working out how a song is constructed is simultaneous with learning it, including the lyrics, for performing purposes. It’s also actually fun, but is that just me not getting out enough? But yes, some songs are just too complex to figure out, but then that probably means I shouldn’t actually be attempting them just yet.