So, what makes GO less competitive and more "pub-friendly:" (I haven't played in a while so some things may have changed)

Uncontrollable recoil - after the first couple of bullets, it seems as though there is no recoil pattern but just a completely uncontrollable spray
Unresponsive movement - key here being *imprecise strafing* -- that is, you want to strafe out a certain amount but you end up sliding out more than you want to. This means that you might expose yourself more than you want to when peeking certain angles and corners and things of that nature.
Unnecessary ambient/environmental factors - for me, it is difficult to see things on the map and distinguish player models amidst all the dust and other strange environmental factors like random vehicles and things like that. This might be a result of my computer not being able to handle the game as well as it should, but I think lurppis described it well when he said it looked like there was "desaturated" lighting, making it hard to see things

There might be other things that I am missing, but these seem to be the most glaring issues for me personally

What makes 1.6 more competitively viable:
The opposite of the three things I listed above: controllable recoil, smooth, responsive movement, and clear maps and textures.

These factors, along with other variables, make 1.6 the competitive, team-oriented FPS masterpiece that it still is today. They also give the game an INSANELY high skill ceiling. The pros of 2003 would not be able to compete with the pros of today. There are still new tactics and tricks being discovered to this day. Not to mention that the individual skill of the average CS 1.6 player seems to be increasing with every passing year.

If you're a non-competitive gamer, you might be wondering why a game must be "competitively viable" to be successful. Let me throw some stats at you:

CS has been around for about 12-13 years now (I believe the first beta was released sometime in 1999). Yet, it is still the most played game on Steam today:

http://steamproxy.net/steamstore/stats/ (Football Manager has more players playing right now but total peak players for the day award goes to 1.6)

The last big CS tournament (Intel Extreme Masters World Championship or IEM) had 70,000 viewers. (This was very recent, maybe less than a week ago) This 70,000 was not the total amount of viewers for the event, but there was at one point 70,000 concurrent viewers for a tournament using an 12-13 year-old FPS game. Sometimes, these numbers even ousted those of games like SC2 and LoL. Also, these numbers were even more insane in the past, when CS 1.6 was truly huge and events like CPL were still being held.

On ESEA (the main online competitive community/league for North-American CS these days), there are currently more 1.6 players playing than Source players. (Though I'm not sure if Source players still play in leagues like CEVO).

It's not that 1.6 players are afraid of change or want a carbon copy of 1.6 with updated graphics (though that would be nice ). We just want a game that will be like 1.6, where one can appreciate the amount of dedication and practice it takes to truly be good at the game. This level of competition results in tournaments, which results in sponsors, which results in more exposure, which results in steady influxes of new players. Sure, the community is not even half of what it used to be; there are no more monthly local LAN tournaments, thousands upon thousands of people playing at the same time, etc. Yet, there are still people playing the game competitively and new players picking up the game every year. It's just that a lot of people have moved on, or are just waiting for the next big, successful installment of the game to revitalize a once thriving community.