That is wrong in so many ways that it's hard to know where to start.
First off, evolution
can't stop - it's going to happen in any situation where you have change and differential survival. That doesn't equate to "survival of the fittest" it implies that "fitness" is a local condition that can (and does) change rapidly. Evolution does not select for strength or intelligence or whatever - those are properties defined by outcomes in different times and places. That's crucial to understand if you want to understand evolution because it's the engine behind speciation! In one environment one set of properties or behaviors may equate to reproductive success that doesn't apply elsewhere.
That still applies* to humans but humans, like many other animals, also engage in other forms of selection than just natural selection. In humans (like others) we also do sexual selection and social selection. So we're selecting on what prospective mates might want (behaviors
or physical attributes) and, yes, our societies also play a role in selection. But you can't just point and say "evolution for humans has stopped" when we observe some societies that try very hard to save damaged infants and other societies that practice infanticide, on the same planet at more or less the same time.** Also, society (and this is what I think you were referring to in your comment) affects survival, but it does it variably because, for some factors, they are selecting as a group.***
We can know for a fact that humans are still evolving because: there are still humans and there is change and differential outcomes. When you say "not just the strongest survive" you are arguing with Herbert Spencer's 1864 conception of evolution, which was incomplete - to say the least. He didn't understand sexual selection, kin selection, or the effect of society on outcomes. It turns out that sexual selection's a big one; it's why peacocks keep growing bigger and bigger fans of feathers: turns out female peahens still go weak in the knees over a big feather fan. And, because the peahens that go weak in the knees over big feathers are the ones that mate with the peacocks with big feathers - you get generations of peacocks that continue to evolve. There's also co-evolution, in which changes in one species cause changes in another species (usually because of a predator/prey relationship) Humans are still subject to
all those evolutionary pressures. That's why there are still male humans that buy red sports cars when they reach a certain age
the difference is that the age is no longer 40 - now it's closer to 50.
We can't help but continue to evolve. When Pasteur figured out the bacterial model of infection and invented sanitation, and Jenner(****) virology, human life-spans began to jump to nearly double what they were prior to those discoveries. One fascinating thing about that is that, as a consequence, you've now got older humans breeding later and later: we are selecting for longevity. We are also selecting out -- this is kind of an uncomfortable topic -- genes for certain genetic afflictions, such as Huntington's disease. It's a fact that many humans with that gene choose not to have children: now that we understand it as a genetic disorder it is being slowly but surely evolved out of our genome. There are other genetic disorders that will likely evolve out, including potentially some of the pre-oncogenes for certain cancers.
It is evolution when parents decide to have an rather than carry a child to term because of a genetic screening; that's the ultimate "differential outcome" right there. The fact that we have people like my friend Michael, who is hale and hearty at 65 who just had a perfectly normal child with is wife who is 52 - they are selecting for long-term health (neither of them has any history of cancer, diabetes, autism, alzheimers, etc - all genetic disorders) I'm not saying that the human genome is improving. Parts of it are, though. Because we're still evolving and we always will be unless we go extinct.
Human society also does some really interesting things that you don't see much in other species on earth: sometimes society creates genetic tsunamis. I am referring there to Ghenghis Khan(1160AD) and Niall of the 9 hostages(~300AD). Ghengis Khan's genes are in 1 in 200 men alive today. About 3 million men carry genes from Niall. That kind of genetic success is unprecedented in nature except for where there is a punctuated equilibrium - we humans did it as a consequence of our social structures, in which we allow successful thugs unprecedented access to lots and lots of females. Talk about "reproductive success" - holy wow! What we may be seeing today is that society provides ... let's say Justin Beiber ... a tremendous genetic legacy because of his ability to rhyme (that probably doesn't say anything about his fitness, though!) the whole notion of "fitness" as in "survival of the fittest" becomes less significant than not carrying the genes for Huntington's or a prediliction for Trisomy-23. But all these are changes. And they are going on all the time. Events push human evolution one way (in some regions) and human society pulls another (in other regions) and so forth; the change is very small and at the scale we live it's literally imperceptible. But we are still evolving.
That is why, in another thread, I commented (when someone was discussing about how humanity will die when The Sun goes into its expansion phase) "In either case the eyes that saw that would not be human." Because in 400 million years (H. Sapiens is about 175,000 years old) H. Sapiens will be gone as surely as the dinosaurs.*****
(* it applies to everything that is alive)
(** in evolutionary terms the time between ancient Sparta and 21st century Britain is insignificant)
(*** you can ask the Shakers or the Amish about how that's working for them)
(**** arguably)
(***** I just had a sandwich including some dinosaur descendant, grilled with rosemary and mayo. we call it "chicken")
Edit:
PS - I wrote
"it's going to happen in any situation where you have change and differential survival" which means that if humans build self-reproducing space robots that are capable of repairing themselves,
they will evolve because the evolutionary algorithm works regardless of what it's applied to. The question is whether there's something that controls/prevents/reduces change over time. There are certain species of worms - I am drawing a blank on the name - that pretty much don't mutate and consequently evolve extremely slowly. I believe the amazing Tardigrade is also a very slow changer, but that may be just because they are awesome.
