platitudinarian
One who uses many platitudes in speaking or writing.
Sir Culling was an extreme Low Churchman, an Exeter Hallite to the backbone, and the head and front of the Platitudinarian Party.
Where it comes from
From platitude + -arian on analogy of other adjectives ending in -tudinarian, from Latin -tūdin- + -arian, the oblique stem of -tūdō.
Adapted from the Wiktionary entry platitudinarian (CC BY-SA 4.0).