Why isn't my phone turning on?!

OK, so here's the thing. I've got an old ass phone (with 4.4.2 KitKat), I've had for four years, so it's been through a LOT. The phone has cracks on the screen and scratches here and there, but for the most part it works functionally. However, out of literally no where, the screen stopped working?

I had unplugged it from the charger and turned to do some work. Out if the corner of my eye I saw it was still “on”, technically it was on the lockscreen since it turns on when unplugged. Thinking nothing of it obviously I pushed the power button to save the battery life and shut off the screen. However, when I tried to turn it back on I got no luck. It just didn't turn on. I removed the battery and restarted it. The screen worked then, I could see it boot up, I even got to log in with no issue, it looked like it was back to normal. However whenever I turn it off, it won't come on again, unless rebooted again and LEFT on permanently. As you might imagine, major inconvenience. I tried looking up solutions but nothing seems to fit my predicament.

The home, back and multitask buttons DO still light up, it's just the screen that stubbornly stays pitch black until the battery is AGAIN removed.

So I'm just wondering, could it be the LCD? The hardware? Should I invest in fixing it or do I just get a new phone? I'm sorta having a low key panic attack because I want it to work out, but I'm just absolutely clueless. Last thing I want to do is break it MORE by doing something stupid..

Anything helps! Thank you so much for your time :)