It's nice to be talking about football again!
I'm not sure I agree with the Micheal Owen comparisons. He joined the Mancs at the end of his career, quite clearly to win a few medals, and apart from a last minute winner against Man City, my only other memory of him at Man Utd is of him fully kitted up ready to celebrate another title win at Norwich before Aguero's winner for City against QPR. He played 31 times for them in 3 seasons, most off the bench and scored 5 times. Coutinho played 52 games for Barca in a season and half, and so far has played 22 times for Bayern. His goals stats (13 and 8 respectively) are not massively different to his time at Liverpool 41 in 152. Roughly 1 every 3-4 games. I must admit, I don't watch the German or Spanish leagues much, so am assuming that quite a few of the goals might have been late in games after coming on as sub, so perhaps some similarities with Owen there. I also agree that based on his transfer fee he has underperformed.
I think what the last couple of years have shown, is that Phil isn't quite at the elite level of our front 3 or a regular starter in an elite level team. Had he stayed, he may well have been in a similar situation. I don't see who he would have displaced from the front 3 and he doesn't have the discipline to play in Klopp midfield, so chances are he would have been on the bench quite a lot here too. Of course, we might not have won as much as we may not have been able to afford big Virg and Becker without the Coutinho transfer money. Getting that much for him was a masterstroke by Klopp and Edwards.
He's 27 now, so going into his peak years, so will be interesting to see what he does next. In my opinion , he needs to go to club that is willing to build a team around his undoubted talent. Arsenal might be a good move, but they might be reluctant to pay big fees/wages post-Covid. Newcastle maybe if the takeover goes through and the new owners want to make a statement. Would deffo be a drop from the clubs he's played for previously, so would depend on whether he's willing to take a step back to resurrect his career. If not, can see him going back to Barcelona.