A great folly here is giving and accepting dose advice based on incomplete information.
[Moi? Vous plaisantez sûrement!]

e.g. I've got an XYZ 18g basket and my shots suck aren't very good.

Firstly, with the same grinder setting, we probably all pretty much agree on:

• dose sensitivity can be as little as 0.1g in some instances
• dose sensitivity can be a gram or more with the same grind and brew pressure for divers coffees
• puffing single dose grinders can makes difference
• it's harder to dial in a stepped grinder
• many hopper grinders require retention purge for all but back to back shots
• ...
• baskets make a difference
• other than level, tamping is largely irrelevant

Which brings us to the Dirty Little Secret hardly anyone mentions:



The Shower Screen

The height difference in these six e61 screens is a whopping 5.5mm. Group to group variation between machines make the permutations astronomical and the likelihood of explicit advice correction infinitesimal.

The leftmost screen in my current inamorata. It's flatter, has the most even across the face flow on an open group* and gives ≈2mm more headspace than its predecessor on its right.
The middle two are Vibiemme OEM, circa 2008 & 2006.
The rightmost pair are puckologist specials to ensure the puck can't expand postmortem. Or???

YMMV

* probably irrelevant, but Hey, could be the Next Big Thing.