"Is it worth it to get it repaired?"

Don't know. But if I remember, the EL had an electronic shutter. Therefore, it's probably not something simple like a bad contact or wire to the battery. I'd be concerned about the longevity of the other circuitry even if the meter is repaired.

Then my rule of thumb is how much would I be willing to invest in a working version of the same camera.

"Am I a sentimental fool for still using it?"

You may be a sentimental fool but not for using a well-made, highly functional piece of equipment.