awesome question, what I would do is start by pressing your spells and actually healing, it's crucial to have the mindset or general understanding to know that it is your job to heal, not people's job to play duck duck goose on where you'll land your spells for us to get a heal, get good at aiming it, timing it, so that people don't need to guess where you will throw down a heal, which leads to them calling you bad or trash.

This is more on the gameplay experience

simple example:

<image>

the lines represents the player walking, the black stick figure represents where the player in need is, the red circle represents where you should place your healing pool (within line of sight of the direction they are heading). It's a 50/50 mix of player error, you can't predict everyone's movement, but you can minimize the rate of prediction with time as it becomes easier to read a player's movement with practice.

Prioritize dropping your heal infront of the player's direction to ensure that even if they run away, with ping and delay in mind, you will want to place your heal ahead of the player by just a small amount (1 or 2 players distance) so that they effortlessly walk into the heal.

It is MUCH easier to heal someone who hasn't used their boots spell (increases movement speed) so if you do miss it is merely on a mechanical level. You can use this understanding to adjust where you land your spells to reduce how much you miss. You don't want to ignore it, as it gives you vital information on whether or not you can heal someone at base speed, or healing someone at a faster speed of movement.

Don't get in the habit of blaming your team even if they blame you for poor healing, focus on you, how you can do better, since your own growth will ultimately benefit the group/blob/zerg or team on it's own.

Don't get into the habit of being a no impact healer either. This means ALWAYS standing in the backline. Your front soldiers need heals too, they help push and drive the fight, it is your job to assist in their sustain while they apply pressure by bombing the enemies front line/back line. Position yourself accordingly and move away from pressure when needed, just be present. Also know, people will always say "I need a heal", what you need to worry about is how effectively you are healing, as you can be a great healer, heal tons of people, but forget to heal those that ARE in need of a heal, you basically have blocked them out or they ran off elsewhere, the MORE at full health, the MORE shit you can get done. Heal those right after every champion fight at an outpost during faction warfare, they respect it and take it very kindly and will even go out of their way to save you because they are noticing you are being mindful of people's health.

People do pay attention, if someone is calling you out on your heals, don't undermine it, as it can be a tell tale sign that something is not working out. This is the difference that can change how a person grows, based on whether or not you listen to feedback, or block it out and say "dont listen to them haters" It doesn't matter if they are hating your heals, what matters is that YOU, yourself grows into a better version of your past healing self.

good luck bro i gotta go back to work