Ivan Perisic and Mario Mandzukic scored as Croatia came back from a goal down to pip England to a place in the 2018 World Cup final.
Croatia had an exhausting run to the semi-final as their two previous games went to penalties and the English media made much of it.
Modric said he and his teammates used the talks about them being tired as motivation to beat England.
"We proved everything different to what the people were talking especially the English journalists,” the Real Madrid midfielder told ITV Sports.
“Pundits from television, they underestimated Croatia tonight and that was a huge mistake and we took it and were saying ’okay today we will see who will be tired’.
“Like I said they should be more humble and respect more opponents and that's it.
“We showed again that we were not tired, we dominate games, physically, mentally and in all aspects. We should have killed the game even before extra time.”
'Best moment of my career'
This is the first time Croatia will be getting to the final of a World up since their debut 20 years ago in France 1998 and Modric says it is already one of the best moments of his career.
“This is one of the best, if not the best but if we manage to win it, it is going to be for sure, the best,” Modric said.
“This is an amazing achievement for us, dream come true, after such a long time, we are in the final.
“It’s the biggest success in Croatian history and we have to be proud. "It means everything. It's a dream come true for us, and all of Croatia," the 32-year-old added.
"No-one gave us a chance before this World Cup, but with our quality, desire, togetherness and fighting spirit we have shown throughout the tournament, we are in the final.
"I think we deserve to be there. From the first goal they scored at the beginning, we dominated the game completely. We were much better technically and physically than England."
Croatia face France in the final on Sunday, July 15.