Visible color of an object looks like something objective — if it looks yellow then it looks yellow, why change it in the first place? I just don't see how this color alteration is useful.

This is the fundamental misunderstanding. Visible color is not objective at all. That sounds surprising if you haven't really stopped to consider or investigate, but it really is the case. Remember the blue/yellow dress?

"Color" is actually a sensation that arises in the mind, not a physical property. Unlike, say, scent, which relies on specialized receptor neurons for each smell, color is largely the result of complex subconscious processing in the brain. Our color perception is very dependent on situation. (In more depth, see this answer to a different question).

So, that's the first thing. The camera can't just show you "true color", because it's just a dumb mechanical device. In some ways, the post-processing it does to create a JPEG mimics human color perception (because, hey, these cameras are made for humans), but fundamentally a lot of decisions are up in the air. This is why white balance is a user-selectable parameter even on the most primitive digital cameras, and on the ones where just about everything else is always automatic.

Related to this, then, is the matter of taste in processing for different subjects. For example, it's usually the case that when photographing people, we want to mute color a bit to downplay skin blemishes. And for landscapes, people often want pushed up colors to make greenery or fall foliage or rock formations or whatever stand out.

Your camera's scene modes are black boxes — you can't see what affect they actually have, beyond guessing from the name and the manufacturer's description. But they definitely do guide the camera's choice in color processing. It sounds like in your case, it also affects the camera's assumptions about white balance (which is fairly reasonable, as a landscape is not normally lit by candles).

If you're not happy with that, it's best to avoid scene modes. The ultimate version of this, of course, is shooting in RAW. You note that your camera can't do this, so it may just have to be a limitation you must accept for — but something to consider for now next time you get a camera.

See also Are scene modes, white balance, color tones, and similar just post-processing effects?