Why doesn't R easily destroy lands anymore?

LD is one of those complicated things.

You need a little, but you don't want a lot.

Heavy LD is a dogshit strategy that loses more often than not and heartily deserves to because it's a deck about being a prick rather than trying to win, but the presence of heavy LD decks are extremely annoying whether they lose or not, which is bad for business.

You don't really need more than three or so decent land removal cards in most formats, usually less in smaller ones like Standard.

Costing it is also kinda wonky. Two mana is way too fucking cheap, three mana usually needs a little something extra to be good, and four mana requires a nice rider to be good.

If you're still here, look up Shielded by Faith. It sounds right up your alley if you're playing "literally anything goes" casual.

...Indestructibility?

Wizards' reasons is that they want people to be able to play Magic instead of looking at the cards in their hand and wishing they could play Magic. Thus, land destruction has gotten more expensive (though almost always with bonuses alongside the destruction itself) so as to not make shutting down Playing The Game as easy.

The power level of a game mechanic can be completely different from the quality of its gameplay.

Stone rain and their equivalents are not very good cards most of the time, but they usually result in terrible gameplay. That's why they are never pushed very hard in constructed.

Contrast this to dual lands, which are often extremely high above the power level they would need to be to influence constructed, yet they have god enough gameplay to get a pass.

Other card types with potentially poor gameplay, even if they are low power.
* Mind rot
* Invisible stalker
* moat

Other card types that tend to have good gameplay even when their power level is pushed
* high value creatures
* planeswalkers
* mana-sink abilities

moat is really good tho