You got unlucky with your devices (having unfortunate hardware compatibility) or the ROM maintainers (being inexperienced or just not good). LOS is really great and rarely has any issues coming from the pure source of the OS.
My experience mirrors yours. I have it on two tablets and they're the most stable and lightweight in terms of a software experience of anything I've ever used.
Motorola dropped support for the moto g within 6 months of me buying it. I got either one or zero android version updates iirc.
“A year and a half of OS updates” rapidly becomes 6 months of OS updates if you don’t buy on launch day, wait for prices to drop a little bit and inventory to normalize, etc.
