My point of view isn't going to be terribly popular.
I went to Plitvice at the tail end of COVID when Croatia was one of the few countries open; but tourism was definitely down. So luckily when I arrived about 10am the park was only moderately crowded. I left my luggage in the honor system luggage room (the honor was that when you got your bags after the hike, you didn’t take anyone else’s bag too.)
Let me tell you, rounding the corner on the path, seeing the first pool was amazing. Absolutely amazing. The second pool, a tad bit less amazing, the third yet a tiny, tiny, tiny bit less amazing and so on. I am going to guess from the stories here that what we experienced as far as the crowd goes it was something like what you would experience today if you showed up at 7:30 in the morning. The families of somewhat unruly children, dogs, selfie sticks, narrow board walks wasn’t the end of the world. After all each pond was ……… never mind. I am thrilled about the first hour, maybe two hours there. Glad for that much.
Split to the Plitvice lakes is about a 3 hour drive. So, for the pleasure of this you are going to spend 6 hours on the road. If you are into the beauty of the place and that outweighs the crowds, just how long do you think you will want to be hiking wood paved trails? For six hours on the road, better be at least 4 hours of pool after glorious pool after glorious pool.
There are two lovely 2 star hotels nearby. And for $125 to $175 a night we opted to pass on spending the night during the planning. That would have made them the second most expensive hotel for us on that trip in Croatia (the most expensive a 4star inside the walls of Dubrovnik).
Basically for your trip of 5 full days (and two half days), you are devoting the equivalent of a day and a half at Plitvice; more than what you have in Dubrovnik. And the cost of that excursion is probably 3 or 4 times more than the cost of any other day on your trip.
Everyone has their interests, G-d knows I am into some pretty offbeat things and spend the time and money to enjoy them to everyone’s dismay. So no judgment there. Just pointing out the time and circumstances that you may encounter.