Sometimes we just have to accept that things are not as black and white as we've seen for years, that technology evolves for the better and gets smaller in the process. Years ago Bluetooth audio would have been laughed out of the room, yet today we have LDAC/LHDC and some others across the board for lossless streaming, whilst audio latency as low as 20-30ms using aptX-LL for gaming/realtime audio use.
There 100% are differences between amps, too, as Rroff says, these differences are often a result of the architecture in the design. R2R and current mode are specifically used in high-end amps and DACs for a reason, they are the most natural/organic sounding with the cleanest signal path, whilst mainstream amps use more traditional architecture. For the last 18 months or so these higher end designs have made their way into compact form factor in stuff like this.
If you haven't been able to hear the difference between various types of amps then either your sample size has been small, or perhaps even your ears just don't notice them, which is also a strong but subjective variable. Doesn't mean a difference doesn't exist, as the people of audio science review will happily demonstrate with analysis graphs of output signals etc, since any audio output can be measured, but a wave graph only tells half the story at the same time.
As for sound colour, that's completely subjective since some people prefer stuff sounding bright/sharp whilst others prefer a more natural warm sound - Which is why some brands are well known universally for one style over the other, there is no right or wrong here, just a preference.
You can also simply look up all of this, it's 2024 and people have already done the legwork with both objective and subjective analysis comparing these specific things in amps and DACs.