Well, they do that, because of you

. Just exploit them. And do the same with suitable hands, if there aren't aggro players behind you. This strategy is not good, because there is no defend vs iso raise. To defend against iso raise, you must limp with all your range. Or with balanced range. With strong hands. But this is a loss of value.
This limp from UTG is more suitable for live poker, because the people don't like to fold. If you play vs many players with your strong hands, this is a loss of value. You can use 5 blinds for open raise. But if there are also happy 3betors behind you, they will exploit you very easily. And this is the adaptation. Limp...With any hand. Even with AA. And you can play wide range (for UTg). With limp-fold, limp-call, limp-raise. And you can use this strategy online, if the table is similar to the "live situation". But do not use balanced range for limp in late positions. Only capped range.