I’ve done fill-in from the beginning
The pre-immersion results compared to a handful of people who started with me, were very much as expected:
My ability to actively recall vocab was substantially better than theirs.
My ability to recognize vocab was substantially worse than theirs.
Reaching a point where you interact with the language, meaning: actually speaking, listening, consuming media etc, flattened it out. I feel like there’s still an edge to it. My reading and listening is still a little behind theirs, and there’s a gap between learning a word and being able to catch it in the wild. They don’t have this gap, they do however have a gap when it comes to using that word themselves.
In short: do you want to prioritize recognition, or recall?
I don’t regret having done fill in from the start, and if I could go back in time, I’d do the exact same thing again. There’s lots of other things I’ve wasted time on, and regret doing, in my Japanese learning journey so far - fill in vocab is not one of those things.
The main reason for this, is that the natural opportunities to train recognition later on are plenty, especially once you start consuming media. The opportunities to train recall are few and far-in between, if you don’t live in Japan.
This is of course my completely unfounded opinion based on a sample size of a handful of people. Take it with a grain of 塩