Replace "serverless" with "managed service" and I agree. But serverless doesn't give you any magical reliability improvement over anything else, because your NFRs dictate the implementation that will produce the most reliable product.

The design of a wooden table will inform what tools will produce the best version of that table. It may not be the newest power tool; it may end up being chisels, hand planes, winding sticks, a kerf saw and a mallet. If somebody maintains your tools for you they'll stay reliably sharp, but that doesn't lead to a good table unless you pick the right tools and use them the right way.