Can a training session have too many different practices?

Yes, a session can definitely have too many practices. Five good-looking activities can still produce a poor hour if the players spend most of it moving cones and listening to the next explanation. At U8 I’d normally rather have two or three blocks that connect. You might start with a 1v1 or 2v2, develop that into a slightly bigger game, then finish with football. The players get more repetition and the coach gets more chance to notice whether anything is actually changing. You can still vary the challenge inside one game instead of constantly replacing it. A useful check is how often the children are actively playing compared with waiting or listening. If they enjoyed the session, nothing is “wrong”, but fewer transitions usually gives you more football and more learning time.