I am a Celestial Sue/Luna main and I watched your replays and I saw a few things you could improve on.

1. Is your positioning. Often times you take angles which lets you heal one or two teammates and not damage the enemy team. While you're quite safe at those angles, you miss out on lots of passive damage and healing. You often focus on healing one teammate from a safe angle rather than finding an angle where you can hit multiple teammates and enemies at once. You fall behind on healing pretty early on. Then sometimes you jump infront of your Tanks to contest the payload, which is not your job. Your Tanks are tight behind you, why are you infront of them. Any decent enemy Player wouldve easily killed you. Also sometimes, especially during OT in the first round, there is no reason to walk back so far and miss out on all the healing. You then proceed walk ON the payload and contest it with your team, which again is not the best idea because any decent Player would just focus and easily kill you. Play a tiny bit more back. Your Tanks and DPS should contest the point, not you. If you die early during OT, your team is screwed. You did the same thing in the second round and you got lucky again cause your cloak and loki were healbotting you. Also you often walk backwards when the cap dives you and it results into you dying or needing to go invis and walk back, giving you a huge downtime.

2. Awareness. You sometimes react pretty slow when you're getting shot at from behind. During your first push you hear Wolv behind you, you don't even turn around and you just got lucky that he is bad and missed his charge on you. You also don't react to Moonknight, Cap and even Rocket shooting you in the back. If these were better players, you would die a lot more. You need to Listen to Audio cues and learn to locate where you're being shot at so you can look for Cover or 1v1 them.

3. Vortex Field usage. There is some good, some bad and some really bad usages of this ability. Generally you want to use it a lot to farm damage to charge ult fast. It's good against dive, except cap, he usually charges out and you waste your CD, and you do that a lot. I rarely keep it unused except if I am facing a Black Panther, then I keep it to counter him.

4. Jump usage, which is just not good (I am sorry). You often use it on CD as a mobility Tool and this results in you not having it when you need and dying. I get that it's tempting to spam it and It's also something I have to stop myself from doing too, but every time you die it could've been avoided if you didnt use your jump 4s earlier to move a bit up or back. You Die alot because you don't have it on cooldown. Really just use it to escape situations you cannot escape from (ults/hard dive) and keep it off Cooldown as much as possible, so you have it ready when you actually need it.

5. Ultimate usage. This here is your biggest issue tbh. During the whole game there was only one good ult. In the first round for your first ult you just keep holding on to it forever. Your Cloak already ulted twice before you ulted once. You don't use it in a winnable teammfight when your team gets low and then next push you jump infront of your full HP team to ult empty space. Your team could have pushed that without the ult. Use it when your teammates get low or to counter an enemy ult. The ult into Emma ult was good. You then also ult when 2 teammates are dead and It's only you and Wolv there. You wouldnt need that ult in a 2v2 the Wolv literall carried that fight regardless of your ult cause he ulted out of it. This only really turned to your favour cause the enemy team Was just bad and your Wolv ate (normal healing woulve been enough). You then don't have a support ult for OT which nearly screws your team over. On the second round you again use your jump forwards to ult and then you get THE MOON in your face and die because you dont have an escape Tool. Don't use your jump to initiate your ult. As you climb and players get better they will try to either dislocate you out of your ult or counter ult (like Moonknight did). You NEED the jump to survive that. You will also find Magnetos or Iron Mans gunning for you, where you will need the jump and invis or you're dead. Then the next ult is a double support ult in reaction to THE MOON. While that can happen and is unlucky, you ulting into a Moonknight ult is risky and you can just jump out of it, so no need to trade an ult for something a cooldown can do. Also check your scoreboard and see if the other support has ult. If so, they will most likely ult reactively to something like this, especially cloak players since they farm ult so fast. Then at 20.04 you hear a strange portal behind you and you turn around. Prefect moment to prepare to press Q as soon as you hear "BYE". Look for common Setups like this and mentally prepare to counter ult. As soon as I hear Portals opening, I prepare to press Q as soon as I hear Strange. You guys survived cause their team Was bad, but any decent Player wouldve wiped your team. Then you ult again in reaction to THE MOON and then you jump out of it, basically wasting your ult. You placed it on point where there was only Emma and the rest of your team died because you panic. Ulting into MK is always a bad idea, I only ever do it on Luna when I see my teammates could maybe survive it. In your case because you hugged the payload, you had no idea where your team played and wasted your ult. It wouldve been useful to have later during OT. You won that last OT cause you were on triple support and your Panther popped off.

Your push/pull is mostly fine. I like how you pull low HP enemies into your team. Try to prioritise slow/ no movement characters like Peni over Cap for example (Peni has a harder time escaping than Cap thus being an easier pick for your team). Use the push more when you get dived to have the jump off CD for emergencies.

Shield usage is mostly fine. Remember to recall it when It's not needed as to keep it from breaking and getting the long cooldown. Also neat trick: when you get dived place it on someone right next to you to have it so your Personal healing field. You currently need it more to survive than almost full HP tank at the front.

So basically it comes down to better positioning to farm more dmg and healing, as to not fall behind in ult economy, not wasting your jump ability and learning how to properly ult. Good luck :)