Sounds like you weren’t using de-waxed shellac. Waxed shellac is for French polishing and topcoats. Gives it that lustre. Dewaxed shellac is for sealing and looks kind of flat when dry. And pretty much everything adheres to it. That’s why it’s such a staple as a “safe” sealer in woodworking under or over all sorts of finishes.
You can buy off the shelf premixed dewaxed shellac. Or when making your own shellac solution, you decant the wax that rises to the top.
The water-based sealers are fine too. But are more prone to making the wood grain swell. And really tricky when using on milled MDF. But when working with waterbased, most shops now just use polyurethane as the sealcoat - whatever they are going to use as top-coat. Saves changeover of materials in sprayers, etc.