Good question, Rio. Practically speaking: your node would stop relaying transactions that have been embing arbitrary data (Ordinals, Runes, $dog and other memecoins on BTC, jpegs) into Bitcoin’s base layer.
You’d still validate all monetary transactions normally. Nothing breaks. You just stop being a free courier for jpeg spam.
Think of it as opting out of carrying someone else’s garbage on your bandwidth and storage — which Satoshi literally said you should be able to do.
https://bip110.org