Desire2Learn appears to be the big competitor now (the university i worked at was completing the migration from Blackboard to D2L when i started. and the Uni System of Georgia followed suit.
That said, during my student years I felt like Canvas was steadily converging on being as unusable as Blackboard, which maybe hints at some underlying pressures in that industry. I was involved peripherally in the decision-making process on a small university purchasing a new LMS, and the decision was amazingly political and driven by niche needs from vocal users, and I say this as someone who was pretty used to university politics at the time.
It seems like the way to get an LMS contract is to throw every feature you can possibly think of into the bucket, usability and quality isn't something that really gets evaluated very well. This probably could be changed but I'm not sure how. For example, the university I was with performed student surveys related to the food service vendor and incorporated the results of those surveys as a performance standard in the contract. Nothing like this was done for the LMS purchasing, no student input was collected at either the purchasing or performance stages, and a combination of purchasing methods and institutional politics meant that faculty input was extremely limited (the vendor was basically chosen before the faculty were invited to provide feedback). I don't think higher-ed IT departments often have a user-focused culture but instead a cost-focused one.
Compared to Pearson's crummy web learning platform and the mess of perl that constituted my college's homegrown infrastructure, Canvas was the bright spot where when things went wrong you could get ahold of someone technically competent and helpful at 11pm the night before your test on Saturday.