Yes, I’m in complete agreement with this post (and with Daisoujou’s earlier one)! I personally think that no one should have to spend 4 hours a day on WK no matter your pace. Even 2 hours is rather extreme, especially at a lower level. No wonder you’re feeling discouraged! There are definitely strategies you can try to help make things easier for you and greatly reduce your daily workload.
Have you read the ultimate guide to WK? If you haven’t, I highly recommend checking it out, and especially pay attention to the tips on scheduling. You’ll probably see your accuracy go up a lot if you hit those 4 hour and 8 hour review intervals after doing your new lessons. You’ll also probably see your accuracy increase from practicing your recent lessons a little more with the extra study mode, or with the self-study quiz script if you want a little more in-depth practice. I’ve spent the past 20+ levels doing the self-study quiz every single day after I do my new lessons to drill myself on the new material.
And yeah, I definitely do not recommend doing 20 lessons a day if it’s resulting in a 20 day level-up pace. It sounds like you might be overloading yourself.
I personally do about 12 lessons a day (and usually 10 at the very beginning of a level and at the end), and I use the lesson filter script to distribute the kanji throughout the level so that I learn 3 kanji alongside 9 vocab lessons every single day. Personally, it’s way easier and way less stressful to me to learn kanji in smaller batches. Ever since I started doing this, my accuracy on kanji reviews has improved by a lot! There are roughly three times as many vocab items as there are kanji in WK, so if you do your lessons with a 1:3 ratio of kanji to vocab, you shouldn’t get too far ahead with one or the other.
Regarding grammar, what helps me a lot (and I’m pretty sure I also have ADHD 
) is sort of using my WK schedule to give me deadlines for my grammar study as well. I level up pretty regularly about every 13-14 days (sometimes a little less, sometimes a little more), and I try to get at least one lesson done in my textbook Minna no Nihongo every level. So far, this strategy has gotten me through the entire first book!
I try to work on at least something in my textbook every day, and sometimes that means doing more work than other days, depending on what part of the lesson I’m on and whatever else is going on in my life at the time. That pace ends out working out to be a little less than two weeks a chapter.
Is my WK pace and grammar/vocab learning pace slower than many others here? Yes. But it’s something that I can keep up every single day, and as long as I keep doing this, I will eventually become fluent. There’s no way to speed your way to fluency in Japanese. Even going very, very fast still requires you to sink a ton of hours into it. Many of the people here who are able to achieve proficiency fast have lots of free time or started WK already with a strong background in Japanese. The best thing you can do is find a sustainable daily study schedule for yourself that you can stick to every single day. For you, that might be more or less hours than it might be for others!