Interaction to Next Paint measures how quickly your site responds when users tap and type, and it remains the vital most small business sites fail. The usual culprits are third-party scripts and page-builder bloat, and the fix is subtraction more often than optimisation.
Loading fast is no longer the hard part. Staying responsive after load is. INP catches the lag between a user's tap and the screen actually changing, and heavy JavaScript is almost always what drags it down.
Audit any struggling SMB site and the same suspects appear: three analytics tags doing one job, a chat widget loading megabytes before anyone chats, page-builder plugins shipping scripts to pages that never use them.
Fix by removing
Open your network panel, sort by size, and ask of every script: what would break if this vanished? Delete the ones without a good answer, defer the rest until interaction.
Then retest on a mid-range phone over mobile data, because that is where your customers actually are, and where Google measures you.