I found a lot of the difficulty I had with remembering grammar went away after I started reading native material. Initially, I still forgot things and had to look up and re-learn the same grammar a few times each, but over time pattern recognition (repeatedly seeing the same grammar in different contexts) kicked in and I was recognizing it without realizing it.
But native material is difficult to start reading because it contains grammar you haven’t learned yet. It requires being able to learn grammar outside of following a textbook.
I think it’s worth giving a try to reading native material and learning extra grammar along the way, as a supplement to continuing going through Genki. This give more exposure to the grammar Genki covers.
To that end, you may want to check out the Absolute Beginner Book Club, which is starting a new manga in a few weeks, then an extra-easy one a few months after that.
This book club is great because the expectation is that you’re encountering a lot of unknown grammar and vocabulary, and you can ask questions, get answers, and read others’ questions and answers, to turbocharge your learning along the way. You can follow along at the club’s pace, or go a little slower if you need to.
Worst case scenario, you decide you want to learn some more grammar before trying the manga again. (But don’t fall into the trap of expecting you can fully understand native material before you start reading native material!)