Atletico Madrid is a club that to be used mainly for business, they're not want to achieve anything and only try to find a potential cheap player, then sell at high price. Barcelona don't have a good financial, it's impossible they would sign Joao Felix. I think he will join in one of EPL club again, maybe Newcastle United, Tottenham Hotspur, Manchester United, those clubs are have a high possibility.
I think Atletico Madrid's style of doing business buying and selling players is almost the same as Borussia Dortmund in the Bundesliga. Recruit young players and give them the opportunity to play regularly for two or three seasons, after which they will be released at a higher price. Individually I agree with you, that ATM doesn't seem to have ambitions on winning trophies either in La Liga or in the UCL. However, statistically in the last decade ATM has reached the Champions League final twice and managed to break the domination of Barca and Madrid by winning the La Liga trophy twice.
About Jao Felix the biggest possibility for his future is going back to the ATM once his loan period is up. Man United and Barcelona seem reluctant to pay Felix the price set by the ATM, as well as Chelsea who are not interested in making his status permanent.