Why are you sure that you need a 1:2 brew ratio? Is this what the coffee you like is brewed at?
Ratio is an assumption of strength/concentration, not a mark of quality/guarantee of good flavour….in fact, trying to pull all coffees that short is going to cause you problems.
Coarsen up your grind setting. start pulling shots a bit longer, maybe 1:3 or 1:3.5.
Don’t be so focused on time, concentrate on the grind setting and the weight in the cup. If you have 15s of preinfusion you can still get tasty cups with another 10-15s on top of that (count the whole shot time, don’t break it down, just do the preinfusion consistently).
Score each cup, doesn’t need to be complicated but give it a number, then average up the number over the last few shots, so when you make changes you can see if the average goes up, or down.
The picture of the shot doesn’t help, you can’t see tasty, there ’is no way to troubleshoot that.
So stick with 18g, record grind setting, weight of shot in the cup, total shot time (but don’t kill a shot by time) & score.
Don’t get into a frenzy and make a bunch of shots in one go, just a couple if the first is not good enough to drink. Report back after each one, otherwise it’s too easy to lose your way with back & forth adjustments and not make sense of what is going on.
If 2.1 tasted best, maybe go a bit coarser, don’t worry what other people do, do what you need to do to get a good cup.