Guests ignoring solid walls is not a bug; the game is designed to function like that. If you do not want guests to walk through walls, then do not build walls on paths or do not build paths through walls. You can use the kerbs to block guests from walking through specific items. It would require additional game code to enable guests to detect collision with scenery, and that would cost considerable processing time which will no doubt have a negative impact on game performance.
The same goes for toilet signs. Guests in Planet Coaster are not designed to calculate (pay attention on) which gender a toilet is intended for. It would require additional game code to make guests aware of which gender a toilet is intended for, and this additional game code would cost something in terms of performance.