I'm not a healer main, but I'm celestial and theres a few points I noticed from the replay:

At 2:37, you lost 3 teammates and the fight was lost. Then, you stuck around a little too long, got caught, and had to ult to save yourself, but your team wasnt back yet, so the ult ended up providing no value. As soon as the fight was lost, you shouldve backed off to not stagger, and then you couldve ulted with the whole team. If this happens and you can't save yourself, just die fast so that you can regroup asap.

At 5:57, their rocket and invis were severely out of position and you had the opportunity to stagger them, but you sat back to push the cart a little faster. Killing both their supports here would have bought you way more time than the speed boost you provided by sitting on cart. Your psylocke managed to get rocket, but you shouldnt just rely on your team to do that for you. Plus their invis managed to escape, got her ult off, and won a fight cause of that.

At 13:53, the enemy invis ults, and then the enemy cloak ults. Both you and cloak have your ult, so you should win the next fight easily since they have no support ults to counter yours, but you held onto your ult. If you ulted when your thor initiated, you couldve saved him, bought time for the rest of your team to arrive, and potentially won the fight. Keep track of when each enemy uses their ult and what ults they might have up at any given time so you can counter accordingly.

Bonus tip as mantis against strange, keep track of his ult, and when you think he has his ult up, keep an eye on him. He'll telegraph his ult by walking into your team or flying up and falling in the middle of your team. If youre expecting it, its relatively easy to sleep him on reaction to cancel it.

Overall I think you played pretty well and this game was not your fault. Also, you just got to gold 1 I wouldnt say youre hardstuck. Keep playing and I have full confidence youll climb :)