If you cant handle playing a lot of tables, fine. But the attitude "You cant make money on multi tabling" is simply wrong. It takes a different approach, and adjustments have to constantly be made, but it has nothing to do with waiting for cards. BTW, I am over 50, so it also not necessarily the "new generation", although it is more widespread among younger players.
Anyway, @OP. IDK if you have ADD, but what you spoke about could have to do with normal mental fatigue or simple impatience. Try to see if there is any connection to your chasing and calling bad and being card dead or having a bad session overall. It could just be tilt, pure and simple, and that is actually what I suspect. (Tilt is much more than just being steamed, if you weren't aware of that already).
If you get bored with 4 tables, but are BE at 9, try to cap at 6. Only play more when you are on your game. If you notice you are making bad calls and chasing, then you are tilting. Simply take a break. It doesn't have to be long. But if you cant rein your tilt in, you have to remove yourself for a while at least IMO.
Try to pay attention to hands you are not in, it solves a lot of boredom problems, as well as making you a better hand reader. Never underestimate how much this can help your game overall.