Comfortably even at 50! Maybe even 40. But you’ve got to keep up with the other aspects of the language that make reading easy: (1) knowing 和語, (2) knowing your grammar, (3) getting familiar with collocations and idiomatic language.
Maybe hit level 30 or 40 and start using some other vocab resources in conjunction with WK. Maybe something for 和語！Because for all the glorious 漢語 on this site, running into うっとり, ずばり, さっぱり–words that are more “Japanese-y” than “Chinese-y”, words that don’t really have kanji–running into these in the wild, can be a rude awakening. There are a lot of them, and they are wonderful! But they are not a feature of this site.
Grammar! Here’s the secret: you don’t have to master it, you just have to get a general feel for it. True story! But you definitely need to master Genki I and Genki II. That stuff is your bread and butter and there is no softening or escaping it. By the time you hit advanced grammar, though–think N1, maybe even a lot of N2–it helps to be familiar with it, but you don’t need to be a Jedi Master for an enjoyable read.
Last but not least, collocations and idioms. Collocations are frequent word pairings. They’re how you know that when you’re talking about an お風呂, you お湯を落とす; you don’t really プラグを引っ張る. Idioms are anything from 四字熟語（一所懸命！）to things like 痛い目に合う. You get the idea. You can buy books on this stuff, slam that shiz into an anki deck, and pound it into next week. You can also just start reading, you know, books in Japanese and pick these things out of your ORIGINAL TEXT and put THAT stuff into an anki deck and things will get easier as you go.
Those are your three! (1) 和語, (2) grammar, (3) collocations/idioms. Study those in combination with WK (which gets you your fourth pillar, (4) KANJI), and you’ll be reading in no time. Prob by level 40~50. Go. Do. Become, disciple of the gator crab.