Instant speed land “destruction”…yep, this was
an Urza’s Saga card, all right. Sunder serves as
the blue equivalent to Armageddon, putting all
lands back in their owner’s hands and making
everyone sad at your table. 5 mana is a bit on
the steep end of the mana curve, but instant
speed makes it more reasonable. And even though
the lands just all return to hand, most people
will be hard-pressed to put their lands back out
before they're forced to discard them. (It could
make some kind of combination with landfall
triggers, but that requires a lot of set-up).
Mass land destruction, for the most part, isn't
a thing that older formats particularly desire
or rely on, thanks to the low mana curves of the
format, but this would be busted if it were to
return to Standard. Even now, it’s a massively
disrupting tool for blue or part-blue decks,
especially decks with abundant artifact mana,
and removing someone’s ability to respond
entirely to you is one of the surest ways to
make sure you have a game in the bag. Just be
wary that a resolved Sunder is the fastest way
to draw aggro…
A blue version of Armageddon? In my Magic: the
Gathering? It's more likely than you think, and
in a way it's even more demoralizing than the
original because your opponent/s get to sit and
stare at lands in their hand for at least five
turns, thinking about all the things they'd be
able to cast if you hadn't played Sunder. It
doesn't even seem to be costed that much more
for being an instant (compare Decree of
Annihilation's cycling cost). Having said that,
there hasn't often been much of a niche for
Sunder in tournament Magic. Aggressive blue
decks weren't common when it was new, and the
more control-oriented decks tended to have a
greater need to deal with creatures than with
lands. If you ever do need this effect, there is
no better choice and there probably never will
be.