It's impossible to generalize over free vs paid in regard to predictability. E.g. a provider I paid for simply disappeared once when I was quite busy while my old free gmail still works. Realistically CF's free tier is more predictable than many paid options on market.
My threat model here focuses on what the provider gets out of the free tier. Cloudflare gets a broad view into activity on the internet for building the models they use for their paid offerings. Free Gmail puts people on a path in to Google's ecosystem with basically zero marginal cost.