San Andreas was great for it's time. But muscle/weight gain was useless/boring. Robberies still exist. I think an issue you are overlooking is the hardware we are working with. You make a full city with graphics comparable to other modern games in 2013 with only 512 MB of RAM and an OS constantly running in the background. Just not possible man. What you want is something possible on Next Gen hardware, not what we have today.
Now, that having been said, there are a bunch of cool things in GTA V that weren't in San Andreas. Sky Diving? Wildlife? Scuba Diving? Tennis with actual mechanics? Full golf courses? There are some things not in V that were in San Andreas as well, but I can live without it. GTA Online isn't even out yet, there will be even more content when it does, so just chill out.