If you're not exhausted after a 30 minute workout that just means you're not pushing yourself.
Even after bouldering for hours to the point of not being able to hold a glass of water in my hand I've never been "so exhausted that the rest of the night is down the drain.", and I'm far from being a genetic freak or a good athlete.
I used to be your average 70kg skinny fat teen, that was 4 years ago when I decided to do something to not end up like all the chubby 30+ years old guys I was seeing daily and who were unable to go up 4 flights of stairs without panting, at some point you have to take decisions for yourself. It's not some bs like "you can be the next Einstein/Musk/Bezos if you try hard enough", there is no luck involved, no barrier to entry. The hard truth is that there is no magic bullet, no quick ways to do it, you just have to get up and move, be it cycling, lifting weight, running, swimming.
It's pure lack of motivation/confidence, once you get started everything falls in place and gets easier. 3 or 4 hours of quality workout a week, even at home, will change your body in a few month and you'll never look back. And if you can't find 3 or 4 hours a week to take care of your most precious physical possession (your body) I guess you have bigger issues to take care of.
I'm currently doing a Texas-method-based lifting program: three-days, medium-light-heavy. The "medium day" is mostly volume with (e.g.) 5x5 squats at 90% for example; I'm zonked after. My light/recovery day I'm only doing 70-75%. The heavy/intensity day it's 1x5 100% (or trying to reach five reps).
Of course if you're going an HIIT program, then yes, you should probably fairly drained afterwards.
You're only exhausted after a 30 min workout when you have 0 physical training. After a few weeks it'll have the opposite effects. As developers our body is rotting away day by day, if I didn't push myself to exercise the most physical thing I'd do most of the days is pull a door to open it.
Even a set of dumbbells, a pull-up bar and a stretch mat will be miles ahead of doing nothing. It's very insidious because you can be passive all your youth with almost no side effects, but all those years of passivity will come back at us when we hit 50, 60, 70.