After all these answers the conclusion is that it is not the concentration in itself that is broken but the way larian has implemented it? And if those aspects, like prone, the annoying ground effects and the way the AI reacts is fixed we will have more fun playing casters and using those spells?
If it comes to that i personally, can live with that. Even if i still don't like it overmuch
This is a bit meta -- but it comes down to how do you deal with perceived problems with the ruleset? I don't actually disagree with @mrfuji 's and @firesnakeaires examples of spells that 5th edition shouldn't have made subject to concentration but I don't think the way to fix perceived problems with 5th is the institution of homebrew rules.
Instead you introduce magic items that correct the perceived problem. Has the same positive effect as a homebrew but is easily ignored, sold or modded away for those who don't like it. And magic items don't create ripple effects through the system. So, if you have a perceived problem "I don't think it's very fun that my wizard's firebolt misses so often" Instead of instituting a homebrew -- surfaces on all cantrips -- you give the mage a wand that fires a single magic missile. Give it 50 charges and you have enough for the mage to do in combat until they reach higher levels.
Same goes for concentration effects -- make a ring of mental clarity if you like and give it the characters.
