There is something really odd about Barcelona indeed. This tiki-taka system was working pretty well in the past and it brought even the Champions League title to them. Those times were Messi's prime time also of course. But some time later something started to go really wrong about this team. Even with Messi's huge contribution the team were still a failure in the end.
Messi's departure made things even worse about their CL performance. Therefore I just think that the same system doesn't work anymore. But Xavi doesn't seem eager to make substantial changes in his strategies. However if they fail in the CL in a similar way this season also then I would start to worry about Xavi's future in this team.
Because I don't think only winning the La Liga title is enough to satisfy the board.
well, next season will be a big proof for barcelona in the ucl where they should be able to reach the final with all the qualities they currently have. Tiki Taka can be resurrected by Xavi as that is their trademark and that could be fine tuned to start him in the UCL next season.