The two major issues here are player agency and game speed. On the one hand, narrating what a PC does to the player greatly increases the speed and flow of a game, which is a super good thing. People can be more immersed and more communally engaged as a party (two separate points) when game speed is increased. On the other hand, narrating what a PC does to the player also can reduce player agency, which ruins everything. Agency is the single most important aspect of any RPG. With a total lack of player agency, you aren't playing a game, you're (singular, for you RPGs-as-collective-literature folks out there) telling a story.
The correct way to do this is to use the GM-directed narration technique to increase game speed without removing agency (or perceived agency) from your players. What exactly that looks like will vary from group to group and style to style. Nonetheless, in my groups' RPGs, regardless of what style we are playing in or the players present (the system really doesn't matter), the following has always worked without fail:
Take things slow the first time
The first time a PC does any particular activity, pay attention to it in detail. Ask the player how the PC does each part of the task and why, even though the task isn't really 'important' persay. Remember what the PC did and use this to build your idea of the PC as the GM.
And then less slowly
After that, a number of times proportionate to the complexity of the activity, the importance of the activity to the character/player, and the likelihood of the activity to come up again, continue to have the player narrate what they're doing but in less and less detail each time, mostly just confirming that the PC operates in a certain manner within the confines of the situation.
Narrate things to the player once you know what the PC would do
The second or third or fourteenth time the player encounters something (whenever you feel ready), unless the player has been very inconsistent in their responses to the situation, narrate to the player what the PC did all the rest of the times slightly adjusted to the current situation. If the player seems happy with this you're doing it right. If not, you need to find out what you did wrong. Once your players are used to this method they will be able to take care of that for you, as, really, it's their responsibility to protect their agency by correcting you if you narrate their character doing something out-of-character. Until then notice if your players have negative reactions to your narration, and invite them to correct you. Remember that your narration here is just a tool to save the group the time it would take for you to ask them what they're doing and how they feel about it, and that their word, if it ever comes up, trumps yours here.
This applies both to actions a character might take semi-passively and the character's semi-passive response to stimuli. Truly active actions (ignoring his pleas, you plunge your rapier through the blackguard's chest) should generally be at least declared by the player, even if the in-character response is obvious (though you may narrate the exact outcome afterwards), and truly passive responses (you see a coin shining in the mud) should always be narrated by you to the player (and most systems have structure to tell you what to narrate in those cases if you're not sure).
N.B. I am assuming your issue with 2nd person narration is well evidenced through your examples; If you are concerned with whether a statement of the form "Sir Tristan is hit by the fireball and thrown backwards 10 feet, falling prone" or "You are hit by a fireball and thrown backwards 10 feet, falling prone" is preferable this is not responding to the issues that would be brought up by that sort of example, which are very different. You can see @mxyzplk's answer if you are in fact having that sort of problem, or ask another question/edit this one.