Melinda
You already plan to enter Europe in Amsterdam and exit from Croatia in just two weeks, plus two travel days at each end and, of course many part travel days in-between.
So, I am pretty late to this party, but I share the concerns many have expressed. You are looking at 6 to 8 countries (Netherlands, possibly Belgium, Germany, France, Switzerland, possibly Austria, Slovenia & your departure from Croatia) in 16 days, including your arrival and departure days.
My thought: Slow down, you move too fast. Try to make the moment last.
Consider one week Belgium/Netherlands. Then straight to Croatia or Croatia and Lake Bled. Skip everything in-between. Look for a flight to connect the two weeks, or possibly an overnight train, though that may well be a major challenge from Belgium to Slovenia. Even the two one-week concept is faster than how we have evolved as travelers. (Travelers, or visitors, rather than tourists is how I’d like to think of us)
This suggestion will greatly reduce your travel days, or at least those days where the travel is more of a chore and less of a joy. By the way, consider what is a travel day. https://community.ricksteves.com/travel-forum/general-europe/how-to-count-travel-days
LATE NOTE
You can keep moving and still explore without changing countries every two days. For example, in 11 days in Croatia, we went to Zagreb, Plitvice Lakes, Zadar, Krka NP, Split (3 nights, with a day trip by ferry to island of Brac), islands of Hvar and Korcula, Peljesic Peninsula and Dubrovnik. We swam, ate too well, rode bikes, briefly went to one museum (in Zagreb) and one church (in Trogir), wandered past a wedding at another church, saw some of Diocletian’s palace in Split and walked the walls of Dubrovnik, rode ferries and bought a ring in Zagreb that my wife gets lotsa complements on. 3 nights in Split, 2 on Korcula, otherwise 5 one-night stands. 6 days on e-bikes.
Do you want to enjoy the outdoors, the shops, the churches, whatever? Or do you want to just blow past them and be able to say “been there, done that?” You can spend time in Ljubijana as well as Lake Bled. Istria or Plitvice Lakes, as well as Zagreb. You can see Bruges and Ghent as well as Brussels. You can see tulips in bloom and windmills, along with museums and canals in Amsterdam.