Well for the time being I would suggest researching and building some of the higher tier defensive structures, they're quite useful!
Yeah, MK. 1 Turrets don't exactly do a lot of damage. The main reason your base was probably torn to shreds was because of white slimes which ignore defensive structures and go straight for the main structures. Since there wasn't enough damage output the turrets couldn't stop them and were destroyed; the following collapse leading to a domino effect of your base being destroyed.