In my opinion Xavi is not really a terrible coach because with what he achieved at Barcelona despite managing a team that is financially struggling he was still able to lift the La Liga trophy. I also don’t want him at Chelsea but imagine what he would be able to achieve with a team that is financially stable. So with that i think Xavi will go to become a good coach in future.
I don't think that Barcelona is financially struggling or perhaps we don't know them as the media potray them. If Xavi is aware of yhe club financial situation, no way they are going to allow him signed Lewandowski and be earning such amount. He was in his prime in Bayern Munich and a great striker but there are other options available for them to look into but yet he went for that and currently earning highest money in that club.
For the fact that a club is declared financially unstable doesn't mean that the club doesn't have funds to run the club but instead it means that the club cannot afford further expenses outside the ones they are already running within the club so if Barcelona can afford an important player like Robert Lewandowski and can still pay his salary and other entitlement doesn't mean that the club has enough finance and if the media is wrong about the financial state of Barcelona then why didn't the club rise up and debunked it instead of keeping quiet and if you check Barcelona during the time of Lionel Messi you will know that the club wasn't as silent as they are now even though the influence of the Argentine international professional footballer also aided the team but yet Barcelona were financially capable so nothing is hidden under the sun, if Barcelona had enough cash i think they would have made some good signings so the financial status of Barcelona still maintains that the club is lacking funds.