Can you respond to a fetchland activation by making the land an illegal target?

Fetchlands like Flooded Strand have activated abilities that say 'pay 1 life, sacrifice this land: search your library for a basic land card...' Crucially, this ability does not use the word 'target,' so it is not a targeted ability and cannot be responded to by making something an illegal target.

Under CR 114.1, a spell or ability targets only if it uses the word 'target' in its text (or in a keyword definition that specifies targeting). Because fetchland abilities never say 'target,' the concept of an illegal target simply does not apply to them (CR 114.2, 608.2b).

You can respond to the fetchland's activation on the stack — for example, you could destroy the land in response so the sacrifice can't happen, or you could use a stifle effect to counter the ability (CR 602.2). But you cannot 'make it an illegal target' because there is no target involved.

Example: Your opponent activates Wooded Foothills. You cast Path to Exile targeting their creature — that's fine — but you cannot respond to the Wooded Foothills ability by doing anything that 'removes a target,' because the fetchland ability has no targets. If you want to disrupt it, you need a spell or ability that counters activated abilities, like Stifle.

In short: illegal-target rules (CR 608.2b) only matter when a spell or ability has targets declared at the time it was put on the stack. No targets = no targeting interaction possible.