Is evolution as reliable as gravity?
Let me parse that. No. The law of gravity clearly states - things fall down. So, when there's these "things" that happen to "fall," it is generally assumed that the direction of fall shall be downwards. Unless, there's alcohol involved... or, another force; or they are "lighter" than "air," or... but it is pretty reliable. Ya trip, ya fall, that's all.
Is evolution reliable? In what sense? That things will evolve? Like sharks and alligators? Or, if there's an environmental niche, will evolution force a mutation? Or will another species adapt? Will Creationists ever evolve?
I'm hardly a specialist in either field, but one began with an assumption and a lucky guess, produced some simple math for workable predictions, had the benefit of being easily observable, and became law. The other produced a body of work that a lifetime of study is insufficient to fully embrace, that tells us more of reality that reality ever did, and is more like "scientific fact" than most others such an oxymoron could hope to describe, only to be dismissed as "mere theory."
Thing about scince, if it's a law, it is either a simple piece of math or a simple statement, and it remains law from lack of falsification. Things generally don't fall up. Yea. That tells us something, we have learned some workable equations. Nice. A theory is actually all science really needs - that way, when things fall up, nothing illegal happens - and a theory of the beauty, complexity, and magnitude of evolution - is not something that can be just summed, nature selects. It ain't about f=ma. It ain't about the happy coincidence that gravitational mass equals inertial mass. It is about us; it is about who we are, what we are, and what we can hope to achieve.
Science that produces equations is great for the engineers. Science that theorizes such things as evolution - that's great for everyone.