It's because apps suck and because you aren't actually making progress. Duolingo, Renshuu and all of that other stuff is dogshit because you don't actually learn through things like multiple choice testing. It is very easy to pass a multiple choice test without actually knowing the answer and if you get the answer correct on Renshuu without knowing it, you aren't going to make progress.
You should also consider your actual study time. If you only spend a few minutes a day on apps then you will NEVER make it past beginner level. You need to study for at least 1 hour a day to get to intermediate level and once you hit intermediate level you won't progress much unless you consistently hit 2-3 hours of study time a day. You do this by stacking your Japanese learning with other tasks. For example you practice writing Kanji as you watch TV or listen to a podcast while you clean. Try to make as much of your study material accessible from your phone as possible so you can easily study while you are out of the house. If you cannot consistently commit 1-3 hours daily to studying Japanese then I would highly recommend you give up.
These are the primary resources I recommend for beginners:
1. Japanese From Zero Books 1-4 (this is an intro to Japanese. Finishing this series will put you at intermediate level. It will not make you fluent. Neither will finishing the Genki books. I do not recommend Genki, it's too unfriendly to beginners.)
2. Japanese Pod 101 Most Common 800 Japanese words
3. Comprehensible input learning videos on YouTube (until you hit intermediate level and can graduate to TV).
4. Kanji Study (Android App) - there is an IOS equivalent. ONLY DO WRITING PRACTICE. DO NOT DO MULTIPLE CHOICE. Group characters into small sections of 10-20 until you master them and then move onto the next group. Don't try to take on 100 Kanji at once. It will be too overwhelming. Make sure you review a lot.
5. Brainscape or Anki (Flashcards)
6. Game Gengo (YouTube Channel) for intermediate/advanced Japanese grammar. Search by JLPT listing N5-N2. Do this after Japanese From Zero 1-4. The creator of Game Gengo has kindly outlined all of the major grammar in Japanese a way that can be studied passively. Game Gengo is the most useful, student-friendly compilation of grammar that I have ever seen.
7. Karaoke for basic pronunciation practice. Find your favorite Naruto intro, sing the song with the singer in the background and try to mimic how they say the words. It's not just the R sounds that are different. Most of the Japanese characters are different from English despite sharing similar letters.
8. YouTube, Podcasts, or Netflix for reality TV, J Dramas, and Japanese subtitles. Try to not watch anime as you get further into intermediate level or you will speak like a classless retard who knows hundreds of words you will never use in daily life. Stick to YouTube and live action content. Also while your skill level is lower, shows that are made for women are MUCH easier to understand than shows like Naruto because shounen anime tends to be full of stuff like complex military or high fantasy terms that you will almost never use in real life as well as a lot of descriptive language that will be too hard for you to understand without being advanced level.
6. Italki for speaking practice. This is to be started at intermediate level. Any speaking practice before you are intermediate is wasted time. Do not skip out on speaking lessons. You will not progress past a certain point without speaking. Make sure the people you talk with have good social skills and make sure they DO NOT SPEAK ENGLISH or make sure they have a very minimal understanding of English otherwise you will revert to English instead of pushing your brain to figure out how to communicate with what you know how to say. Most teachers don't charge that much. Maybe $15-$20 an hour. Learning good Japanese is not free. If you aren't willing to invest money, I recommend you quit because you won't get very good. Do not expect conversation with normal Japanese people to progress you as fast as with a teacher. Teachers will correct you constantly to make sure you are doing things right. Regular Japanese people will think correcting you is rude.
7. Google Vision or the drawing pad on Android Keyboard for finding new kanji that you haven't learned yet.
Do not try to learn Japanese by playing video games. Doing so is incredibly inefficient.
The more humble you are about your skill level, the faster you will progress. If you put things at an impossible level of difficulty you won't improve, if you make things too easy, you also won't improve. You want to try to hit a sweet spot between too difficult and too easy.
Tom Sizemore’s effortless cool and phenomenal character work was an inspiration to all of us here at Rockstar Games long before his star performance as Sonny Forelli in Grand Theft Auto: Vice City. Rest In Peace, Tom