I've read that the fact of this are disputed, but I have always found it harsh to exclude someone from canonization just because they simply carried through on a survival instinct, and possibly even half-consciously. So if I threw some potential saint in the ocean and he desperately tried to stay afloat, he'd be disqualified also? What should he have done, just give up and allow himself to sink like a rock to the bottom in complete submission? If ѕυιcιdє is wrong, it's also a passive form of ѕυιcιdє to not even make an attempt to stay alive. I mean ... unless he scrawled blasphemies on the lid of the coffin, I don't see that as any impediment to his canonization.
Now, he did have many enemies in life, since he rubbed quite a few people the wrong way in that many would have "resembled the remarks" made in the Imitation. Of course, whatever the reason, God's Providence prevented the canonization, and that perhaps for a legitimate reason, i.e. that for some reason he did not save his soul (God forbid) or may still be in Purgatory ... or some such.
Of course, canonizations are not primarily for the honor of the saints per se, but only per accidens, and in order to inspire and edify the faithful. Their gloy consists entirely in the divinely recognized assessment of their merits, so on one level, if he's in the glory of Heaven now, he could hardly care less whether he's canonized or not, as I'm sure that the countless souls who had benefitted from what he wrote redound to his glory far more than would any esteem he received from the faithful. That's actually quite consistent with the spirituality in The Imitation.
I do know that I owe him a debt of gratitude, since when I first receive the gift of Catholic faith around the age of 10, I was greatly edified and motivated by his writing.