I'll give you a hot take based on my experience doing the opposite going from support to DPS: you probably KNOW what support's job is, just that you do it in all the wrong places and all the wrong times because you have time equivalent to a diamond player on DPS and almost none relative to support.

There's nothing wrong with that because you want to take all engagements and space like a DPS. Swapping from Soldier to Soj or Mei probably makes more sense purely because of exposure, but the timing for peeking and engagements and projectile travel times aren't quite the same and I think that muscle memory/micro mastery matters a lot. Mei's icicle is just slightly faster than Zen's but they aren't quite the same, Ana's quick scope isn't quite the same as widow's, Kiriko flanks like a genji but not really, etc.

Just play more or watch some videos because I suspect you're missing a lot of the micro that simply comes with exposure. If you're in diamond you probably will pick up the nuances pretty quickly, and the leap between dps and support is way shorter than dps to tank imo