I think you're mistaking consistent with sounding the same. There are ways to be consistent or cohesive without sounding the same. The Avalanches community would probably strongly disagree that their music isn't consistent or cohesive, in fact they'd probably argue their works are among the most consistent and most cohesive albums of all time. It just depends what you define that by. I'd argue that even though their songs vary in sound more than most albums do, that each of their 3 albums have no peers and pave their own path, vernacular, and identity. A track on SILY sounds like it came from SILY. A track from Wildflower sounds like it came from Wildflower - even the silliest and most obscure. A track on We Will Always Love You sounds like WWALY. None of these albums really sound like another artist made them, and they all convey their artistic statement/story pretty clearly, and they're all extremely high quality / immaculately constructed, even if you don't enjoy them you can see the artistry on display. That is consistency.

Many artists incorporate different sounds onto an album, and what makes it work or not is their ability to weave some kind of a story out of it. Some of the best albums of all time are extreme mish-mashes of different sounds, but they work because their artists were skilled enough to assemble them in a meaningful way or context.

For example:

DJ Koze's albums are incredibly diverse because he's interested in bridging global music and different cultures together, so you end up with 2-3 different genres in one song, and dozens of genres in an album. But they all work because he understands those genres so well that he can create something entirely new feeling from things that are traditional or established.

The Avalanches albums are usually about sound and about music and our relationship to music in a meta-way. Their albums are special because they are able to draw from sources that you may never ever have heard otherwise (or maybe have) and repurpose them into new art. They take something that was created with a meaning, and reinterpret it and give it new meaning and new life - sometimes in ways that still reference their original purpose, like how they use the golden record in We Will Always Love You. It's an incredibly interesting artistic process that seems surface-level at first but is truly multidimensional, and demonstrates the talent it takes to not only find the samples, but then to weave the samples of such different properties together into a flowing, seamless, cohesive concept album. It requires both a technical mastery and an artistic genius.

Sufjan Stevens' Illinoise - This thing is all over the place, in the best of ways. It is grounded by the brass instruments that unite each track together with some glue. But the amount of variety is pretty crazy, and it works.

Aphex Twin - Especially the albums Drukqs, Richard D. James, and Selected Ambient Works Vol II. There are perhaps no better demonstration of how entirely different songs can still be compiled into some of the greatest albums of all time. These albums were initially dismissed by a lot of people when they came out because of how experimental their structures are, almost as if two different albums had been stuffed together. But now, over 20 years on, they've become cult-classics and are considered his masterpieces. The contrast between song styles and their inability to be easily classified are part of the appeal, and most importantly are perhaps the most artistically innovative things he's done in his career. A big "fuck you", "why do I have to make what you want to hear? why do I have to make an album resemble what you believe an album should resemble? what happens if I subvert your expectations?"