I've had this issue (although it's not wifi-related). I have really no idea what it is, but most of the time, just running it multiple times will get it to start up properly. (ie, just spam "launch game") Sometimes a new update breaks something and it happens a lot more often. Try updating yuzu if it suddenly starts happening (it usually updates once a day, so there's almost always a new update)

Another thing is that, if none of that works, it might be Steam Rom Manager. Sometimes it detects a DLC or update file rather than the actual game file, and so the shortcut that gets added into your game mode doesn't actually link to the correct file. It can be helpful to go into properties (press the gear in the game page) and check to make sure the launch options is correct. You'll have to tap the textbook labeled "launch options" and scroll all the way to the right. There, you'll find a file address. Just make sure that the file address is the actual game file, rather than an update or DLC file