The gaming world, which is what I presume they meant, is much different today. The days of clunky gunplay and insta-failing a mission for going 10 feet out of the correct path are long gone and would be tiresome for most gamers.
I think some of this is technological, but much of it is style. There are likely limitations that forced some of those issues back in 2013, but I think it's more down to game design practices. It doesn't take a lot of tech to give you another 10 feet of leeway and trigger a sound bite with a snarky comment from another character.
Hopefully San Andreas is lot better (and given the number of mods available for it, it feels like it would be).
Let's not kid ourselves that either of those things is going to be any different in GTA 6.