Really? He failed miserably at Juventus, failed at Chelsea and now knocked out the of the group stage at Inter. You can make excuses all you want but his overall European track record isn't pretty.
He's an amazing league coach, just his CL record is lackluster.
Let's take a look. His first season in Juve he won the league with a team who hadn't been relevant for years. The year after (12/13) he took Juve to the quarterfinal where they simply faced a way better Bayern team.
In 13/14 is where he underperformed. Juve managed to go out behind Galatasaray. The ruined pitch in the last game had its part in it, but Juve should never have been in a position where it was possible to miss the next round before the last game.
Then his next season in the CL was i 17/18 after winning the league with an average Chelsea team who as exåected got knocked out by a better team in Barca.
Then fast forward to this year where Inter after being average for years has suddenly given Juventus a challenge which they haven't had since they won their first Scudetto. The problem with Inter is they are seeded low and they are facing a better team in Barcelona and a quite even team in Dortmund. Both teams with more experience and Inter even with their lead away against Barca and Dortmund (with 2) ends up losing those games. It's not an upset that Dortmund went through. A little disappointing of course, but not unexpected.
So pretty much 2 seasons as expected one a little under expected and one disappointing season in the CL. I feel 4 seasons where only 1 are way under expected is a little fast to judge a manager.
Like if you take Fergusons seasons between 03/04 to 05/06 United went out to Porto in the First knockout round (upset even though Porto ended up winning), Milan in the First knockout round and then the group the next year and United where a 1st seeded team, but still Ferguson is one of the best managers ever.
The biggest problem with Conte is probably how demanding he is, but if the group he trains is motivated he can really bring in results. Kind of like with Mourinho who also usually has more success his first years.