The result sees Roma reach the quarterfinals 2-1 on aggregate.
“We expect more quality from everyone, not just Roma, but in the end someone goes home, someone goes into the draw, and fortunately we are the latter," Mourinho told Sky Italia.
“This is a team with limitations at various levels, but if a few months ago everyone talked about us lacking determination, the ability to control a lead, the disaster against Juve, that we were winning 3-0 in Sofia and it ended 3-2, now people talk about our ability to resist pressure and score in the final minutes.
“It's a trend at the moment, I think we're now eight or nine games without defeat. I was glad that at 1-0 down, a situation of immense risk, a team might be tempted to wait and play extra time, but not us, we pushed to close the situation in regular time.
“I must also say, Vitesse are really good. There's this tendency only to criticise, but I didn't even know the name of their coach, he's excellent! If a team plays like Vitesse, it's because their coach is excellent!
“It's not that we played badly, it's that they played really well. They had players like Bakker who were moving right, left, centre, causing huge problems.
“Obviously, I am not happy that we played today with many players who will also have to be there on Sunday while tonight Lazio are home smoking cigarettes with (Maurizio) Sarri, but it's because Vitesse are really good!"
Mourinho also said, “It was a bad performance on a technical level, it might seem tactical, but it was technical. We defended well and showed character, but we also pushed hard at the end with El Shaarawy as a third striker, not a wing-back.
“I don't want to say we 100 per cent deserved to go through, but over the two legs did a little more."
On facing Lazio this Sunday, Mourinho quipped: “Now Sarri is at home smoking his cigarette while I go home trying to think how we can recover from this for Sunday."