The problem with keeping a well plumb or straight is that it is more common in recent times to deviate a well for serval reasons. Whether it's doing batch or pad drilling, increasing your reservoir contact surface, etc...
Another major factor to casing failures would just be age and corrosion downhole. A lot of corrosion occurs from things like h2s and salty water contact. This can be improved with corrosion inhibitors.
I think the next improvement could be in the alloy used for casing and possibly using composite materials not prone to corrosion. I've done just where special casing has been used but rarely is the extra cost with it and in recent years with the downturn several companies have leant towards cheaper casing that arrives already with pitting in the threads. Not good stuff and that's before it even goes into the well.
I'm sure there are areas for improvement in the cement side of things but really it's only there to hold the casing in place. And create well integrity.
