I've said this before, and I'll say it again. Genealogy's trading mechanics are really cool. There's all these obscenely high impact pieces of equipment dotted throughout the game and limiting how you can move the from one unit to another is a really interesting way to force the player to prioritize strategize.
One thing Genealogy does that I think few other FE games have managed is managing to make each unit feel distinct in their advantages and disadvantages. The game emphasizes planning and commitment. Because skills can't be learned it makes the units who do have skills stand out more than units that don't. All the best gear can be repaired and traded around, but you have to trade them through a pawn shop, which requires an exchange of gold. You can save yourself some gold by planning for this, to get the gear on the unit you want to have it (let them kill the boss or visit the village, etc.) Or you can plan to get more gold on a unit by having them acquire gear you
don't want on them for the sole purpose of selling it off so they can get closer to buying something else. Each purchase can have a huge effect on a unit's performance, so the game forces you to put more thought into your inventory than you might in other FE games, where your only concern is whether or not you're running out of hand axes.
Alec and Noish are really good poster children for the strengths of Genealogy's mechanics. They are both Cavaliers, both have similar starting stats and growths, but their skills set them apart and cause them to feel completely different. Alec has Pursuit, so he feels way faster and more powerful than Noish, even though he isn't all that different. It's just he can double. Noish, on the other hand can only double with the Accost skill, which is finicky, and can sometimes crit. So everytime Noish does battle it feels like kind of a gamble, because he might only attack once, or he might crit or activate Accost and do as much if not more damage than Alec. Alec is your consistent, but less powerful source of chip damage whereas Noish can blow people away but only sometimes. They're far from the best units in the game, but they're around for the entire first act, they're mounted, and they can use swords (the best weapon type) so they're absolutely worth trying to make good.
You can give Noish the Pursuit Ring so he, too, can get the Pursuit skill, at which point he'll start to feel more consistent, probably even stronger than Alec. You also have the Brave Sword, both of whom make good use of. It can fix Noish's lack of consistent doubling and increases the odds that he procs Critical, or it can be used to grant Alec the ability to quad enemies and wear them down just by the sheer volley of attacks. There's the magic swords, lances like the Horseslayer, and various other stat boosting rings that they can be given to improve any stats you find them lacking in. The Power Ring can improve Alec's attack power, the Skill Ring can boost Noish's likelyhood to trigger Critical, etc. People who say Alec and Noish are bad are just people who've never considered to give them anything other than the Iron and Steel swords they join you with. They're both Cavaliers but they never feel like the same unit, which isn't really something I can say for a lot of the other cav duos across the franchise.
More recent titles have tried to give units personal skills, but they rarely succeed in making units feel to distinct because a lot of the time they are just *bad*. As much fun as it is to have the flexibility to reclass units and build them up as anything you like, having hard limits in place can actually do more to highlight the individual strengths and quirks of your units beyond just their class and stats while also encouraging the player to use the tools they're given well and make the most of them, rather than try to min-max and turn your tools into different tools altogether.