While I’ve never tried iTalki, I had an incredibly similar experience when I first moved to Japan about a year and a half ago.
I was rouhgly level 27 on WaniKani, had completed all of Lingodeer’s content on the time (now labeled as Unit 1, I think), cleared Bunpro’s content through N4 (at the time, they’ve added more to those levels since then), and had even done Pimsleur’s Japanese course levels 1-4 twice each. I felt decent at reading thanks to WaniKani and Bunpro, and Pimsleur had gone fine both times through so I thought I’d be okay when I got here. I couldn’t have known how bad it was actually going to be.
I essentially couldn’t speak Japanese, at all. I understood maybe 30-50% of what was said to me, and I had an insanely hard time producing Japanese back to people even when I did understand what they said/asked.
It’s exactly what Leebo said, and then a little bit more even. It’s not only the muscle memory of using your mouth, but the production of speech actually uses a different section of your brain than listening/reading, which means if you don’t actively practice speaking that skill won’t develop. In theory, it’s entirely possible for someone to reach N1 level while simultaneously hardly being able to have even a basic conversation.
The bright-side is this: just like you had to start somewhere with reading kanji and even hiragana, you have to start somewhere with speaking. It just takes practice and time, and eventually you’ll get better and better. After having lived here a year and a half, my speaking has improved drastically because I’m having to use it every day at work, and in my social life on occasion. Having a basis in reading will help you progress immensely as rather than actually learning what you’re trying to say, you’re just reinforcing your ability to recall that information appropriately in the opposite direction.
Talking to yourself is a great tool, especially if you have any sort of commute in a car (by yourself, obviously), or live on your own. I would advise you not to beat yourself up over your ability to speak, and just keep giving iTalki (or whatever method you decide on) the time it deserves and I guarantee you’ll see progress.