Well thats the scope of understanding u have of IW. Her fields r not generic. Each one is specific to the task at hand and she can produce a field for blocking telepathy... She makes fields that are soft or porous for catching people, fields that are sound proof so she wont be detected, fields that allow sound so she can communicate through them, fields that do or do not allow in heat, fields that dont even allow LIGHT itself through. And yes, even fields for blocking telepathy; i dont think there is a better example than her fighting Psi-Lord. She can also produce a resonance and attack phasing individuals.
Why is anti-telepathy a plot device? If all it took to beat the F4 was a mediocre telepath dont u think Dr Doom would have simply used a morlock to fight the F4 rather than elaborate schemes which involved freeing Tryos, nursing him back to health, and then empowering him with the powercosmic; or stealing and amplifying the power of a Watcher and taking the F4 head on?
Practically everyone in the MU has access to anti telepath tech these days and yet the most technologically advanced super team on Earth should only have it as a plot device?