Genius, is an idea that seems stupid at first, but turns out to change the world. Foolish, is when people think it is a good idea from the beginning.
If you're going to settle a new planet - you're going to bring along bulldozers, tractors, and plows - right? Of course to keep those running you need a supply of fuel, and numerous spare parts, and to quickly begin mining so you can produce ores needed to build replacements, and start with a colony ship big enough to haul around the hundreds of tons steel that make up these things...
Or you could do things the old way and use animals. Feed them with renewable grass, eat them when they break down, produce new ones by just leaving the old ones in a shed together... From the standpoint of mass and ship size, packing some frozen embryos with some artificial wombs, and they take less space than one bulldozer - much less a fleet of dozers and spare parts!
Now you could say there is a bit of a problem with transplanting life like this - humans can put on clothes and adapt technology as they need - getting a spacesuit on a horse is a little more difficult. Most life forms have spent thousands of years adapting to earth, not the "rather like earth" or "just a bit survivable" or "well, at least its not hell or France" exo-solar landing locations.
Enter the brilliant idea "lets make some new organisms - bigger, and tougher, stronger, with eight cup-holders fuel injected V-8s!". B-movie mad scientists have led you astray. It doesn't work like that. We can't just make stuff whole cloth, we can only include other genes that happened to exist before and hope it all works together. They can't customize DNA more than that.
But they can work backwards through the chain of evolution, to prior animals, from other times, be it the ice age or earlier. Pack Mammoths for cold planets, Haast's Eagles for large pest control, Riding Elephant Birds. Restore what was lost, since at once point that goat was an Andrewsarchus, that turkey a Velociraptor.
And that in a nutshell, is why we are eighty parsecs from Earth and hiding in a cave from dinosaurs.