I mean the idea was sound. If every natural 20 rewarded you with a critical hit, then you have situations where a town full of peasants was ensured to be able to score a few criticals on even a dragon. By making you confirm the critical hit, you proved that you were a threat in the first place (or were super lucky to roll two 20's in a row, I guess).
The implementation, however, was clunky. You had to make more die rolls in combat, the critical damage wasn't much to write home about unless you had a x3 or x4 damage weapon (at which case, critical hits were as rare as hen's teeth), and of course, there were many circumstances where you could be denied precision damage as well.
I don't miss it. Mind you, thanks to hit point bloat over the decades, scoring a critical doesn't really feel that amazing to me. Wow, I get an extra 4.5 damage on my long sword attack. Yay.
Sure, some characters (and many monsters) can score huge critical hits, but the idea that critical hits are extreme momentum shifts for some, but are almost a non-even for others just doesn't sit well with me. I don't really know what to do about that, however, since 5e isn't concerned with giving all players equal experiences in the slightest. You want big crits, play a Rogue or a Paladin, or some other class that gets more damage dice instead of more attacks, like, amusingly, a spellcaster's at-will cantrips.
On top of this, WotC designers seem terrified at the idea of someone who could crit more often than 5% of the time, as it's almost solely the province of the Champion (I vaguely recall a few monsters that have a 19-20 critical, but don't quote me on it), as if scoring a critical hit is meant to be something amazing, even though, again, most of the time it's not.
I've made a few enchanted weapons with expanded critical ranges or "on crit" special effects, but they have yet to prove to be any kind of game changers either.