Not sure I’d put Masks alongside Measure of Man or Duet. Or indeed have it as an argument for filler episodes.
Given TNG never had much character serialisation, I’d say filler is more like those DS9 and ENT episodes late on that never fit I to anybody’s arc. Like the holosuite ones. Some amazing ones from DS9. Some less so from Enterprise.
But SNW has a good balance between episodic and serialisation. All this comes down to can they keep up the quality on greater volume. That needs more investment at a time when Paramount is cutting back…