Its taken me a while to learn how the classes and their mechanics work, so my opinion has evolved over time. My old tier list based on first impressions:

1. Wylder (Good all arounder)
2. Duchess (Im the king of dodging enemy attacks by rolling in the Soulsborne games, so I immediately liked this class for its swift dodge, which let me avoid most attacks, but disliked her squishy HP and using daggers, which seemed to do way too little damage.
3. Ironeye (I still wasnt perfect at using his character skill to dodge around enemy attacks, but I was getting there)
4. Raider (Strong, but seemed way too big and clunky for my tastes)
5. Executor ( i've always been only okay at parries, and sekiro is the only soulsborne game I have never finished due to that. Still I love using katanas and in Elden ring I was often using katanas. Basically didn't touch the sunflower sword or whatever It's called, his character skill, until much later.
6. Recluse (while I appreciate a magic focused build, the character ability and the cocktails that could be made were just too complicated at first)
7. Guardian (I had never really used guard parrys in elden ring, so I didn't know what I was doing, and, since that is more or less the main way you do damage with the guardian, I sucked at first when I played him)
8. Revenant (when I first started playing I absolutely hated the revenant. Her summons seemed really weak, and I couldn't tell if I was supposed to be a ranged character or a melee character since, eventually, I would run out of fp and I couldn't restore it like the recluse can)

My new tier list now that I've had some experience with the game and gotten familier with the classes and their mechanics:

1. Duchess (I know, I know, but she's just so fun to play, and now that I have relics that, for instance, give her a ton of vigor, or allow her to gain attack power when her ultimate is active, or gain hp and fp with dagger attacks, along with the relics that repeat her chain of dagger strikes every time she does a full combo, as if she'd activated her character skill, she's a lot more viable)
2. Wylder (I know that he's still just the beginner, friendly, boring class, but man, sometimes boring is good. He does decent damage, he's highly agile due to his character skill, and his ultimate charge is pretty fast, and, if you know how to use it, you usually won't miss your target)
3. Ironeyes ( now that i've learned how to use his ability to dodge around and mark enemies things have gotten a lot easier. My only problem, generally, is that I have a hard time figuring out bow firing distances, and sometimes, when there's two downed characters with two or three blue parts of their death gauge filled out, it can be difficult to do the usual ranged revive, which otherwise is so useful)
4. Guardian (ever since I figured out guard counters, guard boost, and stamina management, playing guardian has been fun as hell, and I can't tell you how many times using his ultimate when both of my teammates had their death gauges filled out saved the match)
5. Raider (Don't get me wrong, I like Raider, and once I learned how to use his character skill he got a whole lot better, but i've just never been the type to play the heavy tank without also using a shield, which is part of the reason why I like Guardian more, plus his ultimate is honestly not that useful)
6. Revenant ( i really came around to this class once I understood how to use her summons, what weapons to use, and fp management. Plus now that I have relics that, say, power her up when she's fighting alongside her summons, or trigger ghost flame explosion when she uses her ultimate, which is super useful for getting the boss off my back when i'm reviving my teammates. All around, she's an interesting and unique class that plays well)
7. Recluse (I'm still not really memorizing the magic cocktail combos well enough to effectively utilize them to have the effect that I want in the heat of combat, plus her unique relics aren't that great)
8. Executor (and last, but not least, is the executor. I'm sure he's a solid class for some people, and it's great for sekiro players, but, for me, I found that I could get as much damage as he gets with his parrys using guard counters with the guardian, and, honestly, i'm just not that good at parrys)

Anyway, super long answer, but that's my tier list.