Fixing the symptom gets the asset running again; RCA is what stops the same failure from recurring. A bearing that seizes gets replaced either way — RCA is the process that asks why it seized (misalignment? contamination? wrong lubricant?) so the actual cause gets corrected, not just the part.
The common technique is asking "why" repeatedly until the answer stops being another symptom and becomes something actionable — a procedure, a spec, a training gap. RCA is worth the time on repeat failures and high-criticality assets; treating every minor fault as an RCA candidate burns capacity that's better spent elsewhere.