A tour can't be disappointed. It is a human emotion. It is a feeling. The people involved in it (and probably the spectators) were disappointed. That means that the people were disappointed but the tour was disappointing. It did not make them happy.
"Disappointed" is an adjective if you use it to describe a noun.
I am very disappointed.
I was very disappointed.
I will be very disappointed.
I am a very disappointed girl.
He was a very disappointed boy.
They will be very disappointed people.
(As you can see, it doesn't matter what tense is used, the word "disappointed" remains the same as an adjective.)
I disappointed my brother.
I disappoint my mother every day.
I will disappoint my sister if I don't buy her some expensive shoes.
(Above, "to disappoint" is a verb and changes its ending depending on the tense.)
It was a disappointing film.
I ate a very disappointing meal last night.
He found the party manifesto very disappointing.
("Disappointing" above is an adjective, used in the same way as it was with "tour" in your original.)
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