I thought I am the only one that sees them that way, I know they have improved in their game a lot but I don't think they are invincible as people see them. I even believe if they have played against PSG they wouldn't have won because of their style of defending. The high line defending is why I don't think they are not invincible because the rate at which they concede is just too much and they won't be so lucky to score as many goals every match. Real Madrid poor performance made it looked like they were invincible, Real Madrid lost all matches against them which was what made everyone think they were invincible.
Next season will be more challenging for them and they won't be as lucky as they were last season. Teams would have come up with ideas to counter their high line and defend against them better.
The discussion isn't about Barcelona being the best ever, but they were the team at semi finals, and seeing how Inter played on the final game, we could safely assume Barcelona could play better than that if they were at the finals. It would be realistic to expect them to not lose 5-0 on the final game.
However, it would also be realistic not to expect Inter to get that bad result normally too, that was their bad day. But saying a team that is at semi finals wasn't good would be unlikely and should be more inclined to say they were pretty good at that moment as well. Flick has done some great improvements on the team, and if they could get Nico too, then this team will be one of the best in UCL next season as well.