Am I saying this would have been better? No - but it would have been less of an abrupt change from the mentality of prior editions, and I've had been worried about the knee jerk reaction to concentration that we saw when the edition was released.
I'm not worried about previous editions, or the people that prefer them. I'm worried about this one.
Like I said, I'm a gray Grognard, and I'm fine. If other Grognards can't be fine, it's because they are too sentimental, and want to play the old game, and not this new one. They should go play that old game. God knows I don't need them at the table with the literal line of new players we have waiting to get a spot at ours.
I'm fine with 95% of Concentration. It's made me a more mindful caster, and much more strategic, knowing I can't just stack effects until I'm unbeatable. Every spell has an upside and a downside, I don't always have an answer, and I'm there to 'stack' the battlefield in one direction to help my allies, not to trivialize the whole encounter by myself.
When I try to think through the few quibbles I have (i.e. Flame Blade is nerfed a bit too much), I see that fixing those edge cases would cause more problems than it solves. So, I just chalk it up to 'Pobody's Nerfect' and be thankful for the rest of the game being so good.
It's better than previous editions, and getting rid of all the stacking is one of the biggest reasons why.