Maybe that's the very reason - Marvell's style is less obviously idiosyncratic. The metaphysical gymnastics are contained and controlled by an urbane technique which connects with more than it departs from the traditions it sits among. In particular the use of rhyming couplets, usually but not always tetrametric, rather misleadingly suggests the gliding wit of Pope rather than the passionate intelligence of Donne. (Most undergraduates in my experience can't bear Pope.)
Yet Marvell makes this basic technique do such an astonishing range of things. My old Complete Poems (edited by Elizabeth Story Donno) starts off with three pastoral dialogues in the Elizabethan manner (one of them, 'A Dialogue between Thyrsis and Dorinda', is really good), and then switches straight into the satirical swing of 'Flecknoe'. Later on there's all the metaphysical, love and more sophisticated pastoral poems, the political poems and so on. In one sense Marvell is more impressive technically than Pope because the same devices are made to serve more than one tonal master. Marvell's work shows in microcosm the transition from the Elizabethans and Metaphysicals to the age of satire; he even writes about it, in a characteristically lucid manner, in the following passage, which undergraduates might do well to read in order to understand the shift in poetic practice in the 17th/18th centuries:
Our times are much degenerate from those
Which your sweet muse, which your good fortune chose ;
And as complexions alter with the climes,
Our wits have drawn the infection of our times,
That candid Age no other way could tell
To be ingenious, but by speaking well.
Who best could praise had then the greatest praise ;
'Twas more esteemed to give than wear the bays.
Modest Ambition studied only then
To honour, not herself, but worthy men.
These virtues now are banished out of town,
Our civil wars have lost the civic crown.
He highest builds who with most art destroys,
And against others' fame his own employs.
I see the envious caterpillar sit
On the fair blossom of each growing wit.
('To His Noble Friend Mr Richard Lovelace, upon His Poems')