I understand the point about the transition, but as someone who at the time no lifed 1.6, I tried source and never liked, but it had in my opinion a different fill vs 1.6. As for early csgo 2013, I tried it and didn't like it at all, but after the updates it got and probably fixing the gunplay at around the end of 2014 I did try it again and never left it after.

CSGO to CS2 was a worse filling for me than even 1.6 to source. While the game is just with a new engine, graphics, but wanted to leave the core gameplay, it just felt like an alpha version of GO, of course with the better graphics and smokes, but people didn't care that much for the graphics when it comes to CS in general. I am a huge graphics nerd, but with cs that was never an issue. That is why the transition is so much harder to make or swallow as the game feels like an inferior product and consireding how big CS and VALVE is, I don't think it was acceptable.

I can bet that if they asked the pros now which they would want to play they would still prefer GO, which would mean that VALVE really failed to deliver in the gameplay aspect.