Yeah that's true! That's why it's often recommended to pair them with Squeak Through! I had no problems with them in my current Krastorio 2 game at all... been using it for something like ~50hs or so until I finally implemented personal bots.
With Squeak Through enabled, the only thing that blocks them completely are walls... you often have to cut a small section of the wall so they can pass again, but that's not much trouble usually, since it's easy to pick up the wall and let the little drone pass and place it again.
The fact that they have some trouble navigating around IMO gives them way more character and it's kind of a counterbalance to how powerful they really are at the start of game! 30 of them can easily build a complete smelting array (6 columns, in my example) in less that 30 to 40 seconds (assuming you have all the mats on you, ofc.)