How do you guys judge how to approach a match?

I’m not great at RTS games and generally seem to suck at competitive games for some reason but I still really enjoy SC2 when it’s not annoying. Sadly I’ve hit a rut and noticed I’m having the same problem in other games too where I seem to always misjudge what strategy or approach to have?

I play Terran and anytime I go bio, it’s too weak. Mech gets me whooped by overwhelming combos of units. Air is the strat I’ve had successes with the most by surviving up to a BC fleet or banshee rush thing. I feel like I’m decent at economy but I can never balance it with units and figure out what strat to go with. How do y’all judge it? Scouting either gets me unit destroyed instantly or wastes my attention so everything else falls behind.

I love SC2 but it’s so frustrating