Tarkin's reason for opposing clone troopers in Star Wars: The Bad Batch runs against all the Empire's logic, in the most hilarious way. The Grand Army of the Republic served with distinction throughout the Clone Wars, and in the end, Palpatine's programming turned the clone troopers into obedient assassins who slaughtered the Jedi at Darth Sidious's command. And yet, as faithful as the clones may have been, the Empire wasted little time in decommissioning them.
Admiral Tarkin had never been a particular fan of the clones, and in the first episode of Star Wars: The Bad Batch he arrived on Kamino in order to conduct an official audit. It didn't exactly go well for the Kaminoans, because Tarkin's main focus was on the Bad Batch - the team of clones with so-called "beneficial mutations" who have served as an elite group within the clone army - but who lack the sense of discipline Tarkin would want from the Imperial military. But, in an unguarded moment, Tarkin also explained his opposition to the entire clone program. It seems Tarkin believed the clone army was simply too expensive, and a mass conscription program would be just as effective but far cheaper.
The logic is absolutely hilarious as the Empire has never once cared about money. It's the same Empire that worked on the Death Star for two decades, continuing its construction even though they had no idea how to power its superweapon. Even as he had his agents continue constructing the Death Star, within a year of Palpatine taking the throne he had begun to convert Ilum into Starkiller Base. Meanwhile, he had droid-manned arms depots constructed in the Unknown Regions, in order to ensure his Empire could never be overthrown. The point is, money was never an object to the Empire - or to Tarkin, a senior figure in the project who would go on to sign off on an awful lot of waste on superweapons.
Given the arrant hypocrisy of Tarkin's statement, he was probably lying. It's likely Tarkin's real issue is one of control; that he does not like the idea of the Empire being dependent upon others for its army. Members of the Grand Army of the Republic were created by the Kaminoans, and while the vast majority of the clones were completely obedient to their programming, the Kaminoans were the ones who did the programming. There is an element of dependency in the Empire's relationship with the Kaminoans, and it is one Palpatine and Tarkin would both find absolutely unacceptable.
Their distrust is actually probably wise; the Kaminoans had a contract with the Republic, but they do not know what to make of the Empire. It is entirely possible the relationship between the Empire and the Kaminoans will end in open conflict - and it will be fascinating to see which side the clones end up on in Star Wars: The Bad Batch.
