Are you just wanting a gradient darkening over the left side?
For that, I'd simply use the Lumetri panel, with a feathered mask on the effect (set that in the ECP at the top of that Lumetri effect) and then use the tonal controls to pull the brights down. You use the feathering for the gradient.
I use the gradient method all the time but there is no need for an adjustment layer. You can use Ye Old Legacy Titling tool to create a 4 point gradient. You can then select mutiply for the opacity. It is super easy.