There are few things in D&D 5E on which the consensus is as overwhelming as on the fact that True Strike is an extremely poor cantrip. As discussed in many places, the main problem is the action economy. As this answer to a similar question puts it, casting True Strike is not so much a benefit as it is a trade off: You waste your action on one turn in order to gain advantage and thus use your action more effectively on your next turn. As has also been pointed out countless times, this is rarely optimal, as attacking twice without advantage still has the chance of hitting twice while the chance of hitting at least once is the same as when attacking once with advantage.
The generic scenario in which True Strike actually helps is when a character needs to put all their focus into making sure that one crucial, strategically relevant attack actually hits. Putting it like that doesn't let it sound particularly magical: the character just takes their time to aim. I really like the narrative and I could imagine very dramatic, epic, and satisfying game moments with this mechanic. However, they do not happen, since they alone are hardly a convincing reason to choose the otherwise almost useless True Strike as one of one's limited cantrips.
Would it be balanced to remove True Strike from the game entirely and introduce an Aim Action that is available to everyone and does exactly what True Strike does (mechanically)?
Because this Aim Action is a trade off that is suboptimal most of the time, I would consider it balanced for my game, unless one of the following questions has a positive answer:
Would it step on anyone's toes by making certain class features or spells (other than True Strike of course) obsolete? Are there any exploits in other scenarios than the one described above that I am overlooking?
A sidenote: I also noticed that the Unearthed Arcana Class Feature Variants include the "Cunning Action: Aim" for the rogue.
You gain an additional way to use your Cunning Action: carefully aiming your next attack. As a bonus action, you give yourself advantage on your next attack roll on the current turn. You can use this bonus action only if you haven’t moved during this turn, and after you use the bonus action, your speed is 0 until the end of the current turn.
Having a general Aim Action and allowing this feature variant would keep in line with the idea that the Cunning Action lets the rogue do things anyone can do, just quicker. Of course, one could say that 1.) it's Unearthed Arcana, so it's not a reference for balance, and 2.) the relation between Aim and Cunning Action: Aim is not as simple as with the uses of the Cunning Action from the PHB, but I still thought this observation could be worth mentioning.