Don't fret about it.
There isn't one universal answer to this, but it isn't really necessary to balance treasure on a character-by-character basis. Here are a few core concepts from my experience as a DM:
Different players are motivated by different things.
Some players really need the shiny items to feel cool, others don't. Don't get me wrong; almost every player likes getting cool loot, but for some players the loot is a major motivation while for others, it's a nice accessory and that's it.
Beyond that, aesthetics can also be a factor. Sometimes players aren't excited about a particular item because it doesn't fit with how they see their character. If you decided to put a really cool magic greatsword in the hoard with the specific intent that the barbarian would use it, there's a chance that player will be unenthusiastic about it because she's really tied to the idea that her character wields an axe. A sorcerer might not be down with that Robe of Stars because even though it's a really nice item, it clashes with his whole dragon theme. Many Warcraft players are familiar with the heartbreak of looting a really good item that's just incredibly ugly or clashes with the character's look.
Different characters care about different things.
Even beyond the players, some characters just care more about their gear than others. This often splits along the martial/magical line -- the more magic a class has available to it, the less items really impact them. This isn't to say there's no impact, just that a mid-level wizard or cleric already has access to a lot of options that a fighter or barbarian doesn't, so it may mean more to the non-magical characters to get an item that expands their abilities into the realm of the physically impossible.
Therefore: Fairness doesn't actually exist.
What these two points together mean is even if you handed out equally powerful, equally useful items tuned to each character, some of the players would feel like they got something really cool and important, while others would just be like "Yeah, it's fine." Being "fair" by being mathematically precise in the treasure shares isn't actually necessary or desirable.
Balance happens in the long run.
Over time, you should have a pretty good balance on the item front without really doing anything yourself. The players should be able to divide up the loot without you either assigning it or virtually assigning it by carefully curating the items in each hoard to match the characters.
That said, I usually do curate my item drops, at least for the more rare ones, but it's usually more for thematic appropriateness than to aim them at particular characters. Looking at the expected items-by-tier chart in Xanathar's Guide (p.135), I typically curate the two highest rarity levels for the tier the players are in, and randomly roll the lower stuff unless there's something I want to plant for specific reasons.
As an example, if I decide the treasure at the end of this adventure should contain one major rare item and some uncommon minors, I'll probably roll the uncommons randomly (or just let the random hoard generation decide whether there are any and what they are), but the major rare item I'll pick out myself. I'll look at the party and think about what they have so far -- maybe the last big item was magic armor, and the one before that was a figurine of wondrous power, so I decide this time I'll aim for a magic weapon, or maybe a cloak or boots. Then I'll look at where this treasure is found -- what's the theme or story of the treasure? If we're in the buried ruins of an ancient city, then maybe I'll plant a Mace of Disruption, still clutched in the hand of the fallen paladin who wielded it centuries ago, his skeleton half-crushed under debris from a collapsed tower. If it's a chest of gear hidden in a spymaster's secret bolt-hole, then I might lean towards Boots of Speed or a Dagger of Venom. I don't ignore the party entirely though -- Flametongue is on the list, but if nobody in the party really uses a sword, I'll skip that one.
I also will listen for -- or even directly request -- hints from my players about what kind of items they want. One of my players isn't enthusiastic about magic weapons, but loves magical clothing and accessories, so I make a note of that and will make sure to include those kind of items regularly.
But keep an eye on who's taking what.
Some players can be grabby, and some aren't eager to speak up if they're getting ignored. Keep an eye on who's getting what loot and who isn't. If somebody is routinely ignored, make an effort to get an item in the game that speaks directly to them, and if the players try to redirect it, you might even speak up to mention that it's a really nice item for the Ranger or what-have-you.
