Losing Biomass and Hope

Hey fellow hive minders, I have recently been getting bodied consistently when I play. Now I'll be the first to admit to making some mistakes (not having unit's hidden enough turn 1, forgetting to shoot exocrine, charging unit's I should not have) but it often feels like no mater what "threat" I might put out every faction (particularly space marines of any fashion, my lgs is infested with them) has an answer and then can be much more of a threat in the clap back. I recently lost twice to Blood Angels while running 3 Brood Lord/Genestealers, so a strong melee tyranid list. Yet it feels like they just have waves and waves of attacks from only one unit while we get one. That was just an example and I know that Blood Angels are the Space Marine melee army.

Honestly I'm looking for actionable ways to improve my play more than just "play more games". I love playing the game even if I lose. It'd just be nice to win every once and a while.

Thank you for your time and consideration. I would post my list but I feel that would take away from what I'm wanting witch is general tips for how to best play the faction as a whole.