Hey there, you've raised alot of stuffs that I would agree to actually, except maybe I would like to say indie is basically anything not on a major label, so technically, local bands can call themselves indie.
However over time, indie has developed its own sound/music such that it doesn't merely mean independent label anymore. And so, we tend to classify if a band is indie or not based on the music they produce. If going by that meaning/definition, then I agree that most local bands are not indie.
The ironic thing is that, our local music industry needs more coverage and appeal to the locals. The indie community is significantly smaller than the mainstream here. And so, if local bands want to survive long enough, they have to branch into mainstream, like Electrico which sounds radio-friendly yet alternative, but not too indie to me. If they remain indie-sounding, they become even more obscure in an obscure community, which doesn't help the situation.
I think basically, if a band wants to succeed, they have to stand out, and not sound like everybody else, which I feel is the current situation in Singapore. And if you noticed, for overseas indie bands, they also incorporate an interesting variety of musical instruments, something which you don't see in the local indie scene. Hence, the lack of an "indie sound".