In my opinion it's the other way around.
Reading is easiest in any alphabetic language. Both intrinsically and to teach.
Reading has no time limit so you can make your way through text at whatever pace you want.
Reading instruction is strongly amenable to automation. You can just sit and do exercises on an SRS until the cows come home and you will eventually learn to read. Not on duolingo through.
Speaking is the next easiest, you can't go at any speed but you can at least go slowly. Plus you only have to deal with one accent when speaking, your own.
Most languages have more consistent spelling than English, so if you know how to read an IPA phonology chart (and if you are embarking on the multi-year journey of learning a language then spending a time to learn IPA is a no-brainer) then you can probably figure out how to speak in a way that is understood.
Listening is the hardest because you don't control either the content, the pace, nor the accent. If someone is throwing words out like a gattling gun or in a non-standard dialect then tough luck. The learning curve for listening is a cliff in most circumstances.
Neither speaking nor listening are amenable to automation. TTS is no substitute for native speakers, and automatic speech recognition is a joke. So the only way to pick up these skills is with real native speakers which is expensive and slow.