Unlike most of the formulaic "rock" bands of today who are required to write the same drivel over and over ad infinitum.
One Nickelback song sounds like every other Nickelback song. The chord changes might differ somewhat from song to song, but stylistically, tonally, they are all nearly identical. Ditto U2, REM, Creed, Nirvana, and especially RAP by any RAP "artist".
Even when some groups do covers, they sound the same: GnR's covers of Knockin' on Heaven's Door and Live and Let Die, for example.
No one can claim that Eleanor Rigby sounds like Why Don't We Do It In The Road, nor that Helter Skelter sounds like Here, There, and Everywhere.
(flame suit on to protect from those whose favorite ox has just been gored)
They might have refused to do the same song twice late in their career. But they built their empire on cranked out clone love songs:
Love Me Do
Please Please Me
I Want to Hold Your Hand
Can't Buy Me Love
Eight Days a Week
...
Heck Paul just about admitted it in "Silly Love Songs" when he had Wings. And that's the part of the Beatles catalog that keeps me from every being able to rate them higher than a C-. These are the guys that INVENTED formula pop, just because they eventually moved on doesn't forgive them their sins. You want to know why all Nickelback songs sound the same? Because the Beatles proved that making the same song over and over was a license to print money.