I would argue the exact opposite, but it's because it's not only just the product, but also the customer service and experience.
Switching from Amazon to a similar service is a huge risk to me. Will I get the same customer service when I order something and it comes shattered at my door? Can I rely on two day shipping being really 2 days? (I know some people here are whining about it being 3, the majority of us get it within 2, sometimes 1) Can I trust the reviews on the other sites? Will they know my preferences and suggest me other items or books as well as Amazon or are they coercing me? Do I get the same value added from the "premium" subscription such as Prime? Who knows.
Switching cloud providers? A snap, provided you have architected your systems according and not treated AWS offerings as black boxes and understand "OK I am using RDS, I can just switch to another MySQL provider easy enough" and prepared accordingly. "Ok I am using Elasticache, time for Redis." I imagine it's even easier if you stuck to containers. And unlike Amazon retail where there really isn't an online store that can match it in terms of customer service and experience, many would argue that a DigitalOcean or similar have better customer service, so there is competition there.