Vapider is the comparative form of vapid, meaning more dull, bland, or lacking in substance.
Something vapider than another thing is even more insipid or uninspiring: Each sequel grew vapider than the last.
The word is uncommon; "more vapid" is the usual construction.
1. intellectual — duller, More lacking in edge; blander (More lacking in flavor); emptier (More devoid of contents); shallower (Less deep comparatively)
2. expressive — blander, More lacking in flavor; flatter (Praise to please)
Opposites
intellectual stimulation and substancevapider ≠ deeper More extended inward; richer · weightier · meatier
interestingness and engagementvapider ≠ livelier Having increased vitality; zestier