This has been widely discussed in the Instinct forum: https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/instinct/217597/turn-by-turn-navigation
Courses created with Explore do not provide turn by turn navigation, at least when used with Instinct.
Here is my Instinct when I navigate a course created with Garmin Connect.
As you can see, the arrow in the upper left tells me that after 81 meters I have to turn left. When I reach the waypoint (labelled "punto"), the arrow tells me it is the moment of turning left.
Here the same course, but created with Explore. No arrow, as you can see.
And when I am 18 meters from the waypoint, the watch tells me that but, again, no arrow (in the circle inlet, in this case).
Instinct v4.60, Connect v4.29, Explore v2.8.3.