For Barca, who went out on away goals to AS Roma in the quarterfinals previous year after winning the first leg 4-1, it was a bitter night that will raise many questions for coach Ernesto Valverde.
They lost the first tie 2-0 before clocking up four goals in the reverse for a 4-2 aggregate win, and then required a superior away goal count to see them through in a 3-3 aggregate draw with Paris Saint-Germain.
The Barcelona talisman has been in the form of his life, scoring 48 goals in all competitions and creating another 22.
"When it looks good, it's good and Messi gets all the plaudits".
"Once again we showed that everything is possible in football", said Wijnaldum.
"Liverpool have been smarter than us, they were faster".
Even at 3-0, Liverpool were still at the edge of a precipice the whole time, because just one Barca goal would have left them needing two more goals to go through.
Many were visibly moved by the experience and some could not hold back once they had reached the sanctuary of the dressing room, especially after suffering heartbreak in a weird final against Real Madrid in Kiev nearly 12 months ago.
"We knew we could do it and trained very hard for this night". Fabinho followed that up with a crunching tackle on Luis Suarez, who was jeered and goaded relentlessly by Liverpool fans at the ground he graced for 3 1/2 years. In one incident, the striker flicked his boot back into the right knee of Robertson as they ran along together.
After they had trudged back to the dressing room, it was apparently all too much for skipper Messi, who broke down in tears, according to the Guardian.
Wijnaldum's impact after coming off the bench of the second half can not be understated.
If his first, prodded through the hands of Marc-Andre Ter Stegen, was slightly scruffy, his second was sublime: a header beautifully guided into the top left corner from Xherdan Shaqiri's lofted cross. You've got a player there like Coutinho who when he was at Liverpool excelled at times, looked a brilliant player.
Then came the coup de grace after the cheeky play by Alexander-Arnold at a corner.
Valverde, whose team gave up a 4-1 first-leg lead against Roma in the quarter-finals last season, refused to make excuses after the extraordinary exit.
Liverpool booked their ticket for the final on 1 June, with their opponents to be determined between Ajax Amsterdam and Tottenham Hotspur on Wednesday night.