What I've started to notice as I get better and play against better players is that people tend to go a lot harder in lane phase and fight a lot more. As someone who always enjoyed playing defensively and getting a 10+ CS lead as a result, it started to irk me when I'd look at other solo lanes with 3+ kills. They were farming terribly, recalling constantly from their ridiculous fighting, but they were full levels in experience and tons of gold up on me to a point that my impact on the game was insubstantial.
I started to realize that you need to gain a bigger advantage over your lane opponent than a simple CS advantage. I dropped all my scaling runes, went to flat, and I've started to play a lot more aggressively to hilarious effectiveness. As a result I've learned a lot about lane power spikes for the champions I like to play and I'm learning when I can afford to go stupidly aggressive in lane, and it's really paying off. I'm carrying games a lot more often instead of being an average bystander at the whim of my 5 kill (or 5 death) teammates who went hard and succeeded/failed.
As far as people who leave objectives for CS, yeah for sure. Obviously it's more situational though. Sometimes a big wave is worth more than a kill, dragon a lot of the time isn't worth a fight if your teams behind already AND missing a big minion wave for it. Also consider that pushing the wave gives you map control and allows you to take more objectives if you win a fight.
EX: Just yesterday I was clearing a wave of about 500 gold in minions bot lane, our inhibitor tower was down and that wave would have taken the inhibitor. Our ChoGath managed to get caught trying to ward baron and started flaming me because I wasn't there. I made it up in time to deny their baron attempt, but for him to assume it was my fault he got caught because I was farming and doing something productive is just silly. Especially considering he could have just waited for our ADC who was on his way with scrying orb to check it out.
If you have a player off solo farming, don't go into a position where you can be engaged 5v4! If there's an objective that you need to contest, only do it if you're sure you can disengage safely. If someone is off farming, maybe they're making a mistake, but that doesn't give you an excuse to throw the game because of it.