Minecraft Java Edition – Is It Possible to Obtain Ice in Superflat

In more recent updates, you can see in advance what your enchantment will be (at least in part) AND it also randomizes after accepting an enchantment AND it allows the exchange to cherry pick enchantments.

By bringing a bunch of rubbish items to enchant in addition to your one diamond pickaxe will allow you to enchant the pickaxe only when it is silk touch. Via exchanging say an iron hoe with the pickaxe and lesser enchanting that instead will randomize again allowing you to try again with the pickaxe. Of course you would use levels to enchant the garbage items but doing lower enchantment will use less levels allowing for more tries.

So where you used to need 150/180 levels to try 6 diamond pickaxes you can look at dozens of tries for the same number of levels.

No, you still need a pickaxe for ores.

From the wiki entry on silk touch (emphasis mine):

Allows the collection of normally unobtainable blocks such as Ores , Grass , Mycelium and Huge Mushrooms . A pickaxe must be used for stone-based blocks (ores), while any tool can harvest grass, mycelium, huge mushrooms...