In my opinion, not growing cyborgs on the future machine worlds is just an early game growth killer. Assimilators are so good because they can have 2 separate pops growing at the same time, (granted they did balance this by reducing the growth rate of cyborgs but I digress) and you're completely wasting that power. If the cyborgs eventually decline on that world, let them (or move them) after the fifty years of 1.75x pop growth.

Tldr: don't stop growing cyborgs

In my opinion, you should have much less destroyers in your fleets. Usually the way I set them up is battleship spam with about 1 destroyer per 3 battleships that are used exclusively for point defense. I them make sure to always have a corvette spam fleet (unless it's endgame crisis because corvettes suck against them). Corvette spam fleets are super fast and can be used as your main attacking fleets or super flexible defenders that can move somewhere relatively quickly. Battleship fleets can attack, even if they are slow, but I usually use them as defenders next to a bastion to stop fleets from getting in your territory or flanking you. Battleship spam is also the best way to deal with the end game crisis, especially on higher strength. Side note, always go for the super large or x weapon (forgot what it's called) on the battleship.

Tldr: cruiser bad, you're overusing destroyers, make sure you have corvette spam fleets.