Before my first trip to Japan, I tried teaching myself basic hiragana/katakana characters so I wouldn’t be entirely useless. It didn’t work. You can learn characters with flash cards, but unless you learn words and grammar as well, those characters aren’t much use.
OTOH…
I’ve been hammering on Duolingo for about a year and a half now in an effort to learn (very) basic Japanese. My wife, born and raised in Japan, tells me that it occasionally is wrong in pronunciation (kanji characters are pronounced differently in different contexts), and that it sometimes utilizes kanji characters that hardly anyone in Japan uses. Despite those flaws, its “gamification” (the scorekeeping, competition, colors/lights/sounds and positive reinforcement) of language instruction, together with the incredible convenience of accessing it on my phone, is the thing that finally motivated me to start learning and to stick with it. We visit Japan at least annually, and while English is fairly common as a second language on signs and in spoken interaction, it is by no means universal; I’ve been very reliant on my wife to provide translation services in the past, and my hope is to become a bit more independent, for the convenience of both of us. During our last trip (before the pandemic), it was pretty cool to walk up to a sales clerk and be able to say “I bought these glasses here yesterday, and I would like another. Do you have more?” Probably with shit grammar and pronunciation, and bereft of appropriate honorifics, but he was able to understand me so I’m putting that in the “win” column.
So far I’ve earned about 520 crowns, with about 200 left to go before I’ve completed the entire Japanese module. I worked my way up into the diamond league after a few months, and have stayed there ever since (it’s easier to stay in than it is to get in).