Obvious concept of concept album is obvious.
It's really amazing that, amidst the social media cacophony of "Gilmore is not Floyd!" and "It's not Floyd without Waters!" #putdownthefuckinghammeralready and Gilmour and Mason specifically stating exactly what this album is supposed to be, so many have missed the point entirely.
If that wasn't enough, they were pretty heavy-handed with the naming scheme. (The music is) "Louder than Words" is about as obvious as it anything can be obvious. Aside from being a direct barb at Waters, it does pretty much sum up the whole concept nice and tidily.
"On Noodle Street" is simply a bit of self-deprecation on Gilmour's part and his way of owning up to the primary criticism of the so-called Gilmour-Floyd Era.
And the short "Unsung" is clearly meant to be a posthumous heralding as it leads right into "Anisina" which plays direct counterpoint against Wright's masterwork "The Violence Sequence," which ultimately became the climax of the band's most coveted work.
And how does one plagiarize oneself? Every artist in existence, regardless of medium, has a finite pool of ideas he or she draws upon. Hell, look at some of the most famous/prolific film composers of the last 50 years; most of them have reused whole melodic passages more than once. But you'd never call it plagiarism. More importantly, sounding a bit like one did in the past is a fry cry from recycling old material note for note.
But once again: the musical core of Pink Floyd sounding like the musical core of Pink Floyd was the whole fucking point!
And saying you "could hear essentially every album they've ever made" is a bit ridiculous. Tonally, it mostly sounds like TDB, which is understandable since, you know, it's the other half of TDB. And there is a clear difference between what Gilmour recorded back then and what he added now--since his guitar (wood), pickups, and amps are all different. "Surfacing" is obviously a new one since it sounds like it came strait off On an Island.
There are only two songs that sound like old songs. Both cases were intentional.
"It's What We Do" (All three of us.) is another name gone obvious. It's the song that sounds most like an old song, the band's capstone: a nine part opus that spans 25+ minutes and consists of three short verses. For which, the other guy gets all the credit and he basically just wrote the three short verses.
The other one is "Allons-Y" which is a double (triple) entendre of a name. (Let it marinade for awhile.) It's Gilmour reminding everyone that he was there too, by reclaiming his signature guitar riff from Kilminster and his fucking hair flip.
The song is broken up by "Autumn '68" that is a reminder that, despite Wright's untimely and unnecessary departure during the Waters era, there were a few short months were Wright was the de facto front man. The haunting pipe organ (recorded droning that time) breaks down the wall--sort of speak--as if Wright is calling out from the afterlife not to so easily be dismissed. It's haunting and the pinnacle of the album.
The Endless River is really the three securing the respect they've long been due. They are saying that Pink Floyd was not just Waters--quite the contrary. In fact, had it not been for them (Gilmour, Wright) "Wish You Where Here" would just be a forgotten overly sentimental poem buried in Waters's closet behind the suitcase of the left. The album is a reminder that, as a listening experience, Pink Floyd has all ways been first and foremost about the music, and, as the core creators and contributors to the band's sonic identity, they deserve way more respect than they're given.
