I'll actually be the one to respectfully offer a dissent here, I suppose; so far as I'm concerned BUMP have been trying more with their sound lately than they have in... a fairly long time honestly. The amount of vocal effects, electronic touches, and overall layering to their music has increased by a not insignificant amount ever since "RAY" released, and I really support them heading in that direction. This doesn't mean I'm not going to criticize "Hello, world!" in particular, however, for drawing far too much on "Karma" for its own good, but "Parade", Fighter", and "Colony" have all done things which they've never really tried in the past or haven't done in a fairly lengthy period of time. You could also see a fair amount of variety on "RAY" if you actually take it track-by-track and in terms of overall progression (electronic -> acoustic). However, and I hate to use this in my reasoning, I also have a fairly expensive audio setup (not crazy, but I've sunk more than a few hundred dollars into my current listening array) so I can actually hear every bit of what's going on in each track, which might be giving me a bit of a different perspective on all of this.
I generally consider "COSMONAUT" to be the trough in their creative career, since while it absolutely did have some tracks that were worth listening to, I think it's the weakest overall album they've released since "Jupiter" (and yes, I'm actually one of those people who finds that release inconsistent). "COSMONAUT" isn't a bad release, but it just lacks a real sense of flow, cohesion, and innovation as compared to some of BUMP's other records. What I will say though, is that Motoo does use a fairly distinct singing style for it (if you pay attention, there's been a bit of shift in how he sings on every full album since "Yggdrasil", which is an intriguing little detail). As things stand right now, I want them to continue experimenting with electronics and vocal effects, since I think that's probably the direction they're going to head towards in the future, and the one that stands the best chance of differentiating their next album from what they've done before.
Ultimately, all of this is just my opinion, but I'm honestly pretty happy with where BoC are musically right now, and of course lyrically they're still some of the very best in the industry, which is always an additional treat to look forward to.