I mean, if you want to use spells that rely on concentration - build your character around them. Spells are not the problem, your builds are not suitable for them. I've played a sorc recently that was built purely for concentration spells, he had +5 CON ST with advantage and I was hit, burned and blasted while my Blur and Enlarge remained intact. Any class with a CON ST proficiency or any race that allows you to reach 18 CON helps. Another way of building a concentration focused character is to make him a sneak - pop a spell and hide, your concentration is protected. I bet you are talking from your experience, try my solutions to concentration problem if you want, I think you'll be surprised how well it works.
The spells are the problem at least most that have concentration ... It's concentration and how it limits your spells choices. Not how it works mechanically even if it's boring and prone to exploit but i can live with that part, the part you are talking about.
THe problem starts with how you can only have one concentration at any give time. Better spells will use that concentration and edge case spells will see no use. Just means less spellcasting and less fun for the player. Reason? Damage is always king in video games especially when primary armor system is avoidance like in DNd with AC.
EA data would show that nicely.
LIke i said, it forces the player in this cookie cutter setups of optimal play and casting the same old spells over and over.
Example like ranger or any other class... YOu need Hunters mark to get max damage so there is no point in ever using other spells that will give you less damage or advantage you can get those effects 100 other ways. That don't use up resources.
IF we talk about keeping up concentration ? Well it's too easy, you don't need Con at all. AI isn't smart enough to focus fire on it anyway. Players can just hide or simply brake line of sight and you are safe.
