As has been said by @fev in his comment, it depends on context. "Luxus" is of latin origin (who'd have guessed that?) and Latin had actually two words:
Luxus meaning "luxury" or "excess"
Luxuria meaning "rankness" or "offensiveness"
In English "luxury" originally meant "lechery" or "lust". For instance, Shakespeare:
She knows the heat of a luxurious bed.
Her blush is guiltiness, not modesty.
Much Ado About Nothing, Act 4
Over time the meaning changed from purely negative to also mean "sumptuous" or "opulent". But still, it can be used in a negative way, connoting "extravagance", "prodigality", "thriftlessness", etc..
That doesn't mean it has to have that meaning. "Luxury" (or "luxurious") can also be used as synonym for "gracious", "lavish(-ness)" and so on.
The basic question is: if someone uses a lot of resources to accomplish something he could get for less, is that (always) a bad thing or could it be a good thing too? If I have my toilet bowl gold-plated, is that just wasteful? Or might there be some aesthetical goal at play which any other material would fail to accomplish? And isn't painting the walls the same? After all, the reason for the walls, the protection from cold or weather would be accomplished by unpainted ones too, no? So, is the golden toilet bowl lavish, luxurious, indulgent, opulent? Are the negative connotations just the envy of the ones not able to afford it?
You are the judge.