See the accompanying photos for these articles to get an idea of what Pope Francis's daily mass at Santa Marta is like:
Pope Francis at daily Mass: the fruitfulness of praise
Pope Francis at Mass: bishops, priests ordained to serve
Pope’s Santa Marta Homily: Christian mediocrity leads to a ‘loss of sense of sin’
Now it can be said that the pope's private Mass has been "low" for quite some time, and this was true of Pope Benedict. (I can't remember if there was an option to celebrate ad orientem or not, and if there was an option rather than ad orientem being necessary, if Benedict preferred it.) But it was rare to see a photo of Pope Benedict's private Mass, which was attended by a select few. Pope Francis has allowed photos to be taken and attendance has been opened up to certain individuals and groups. His ars celebrandi is an example for the Roman rite, whether intended or not.
Does a low rather than solemn Mass save "time" for the bishop of Rome, who is a busy man? And does Pope Francis' health prevent him from singing? Regarding the second question, even if he cannot sing recto tono, this does not mean that other ministers (such as the lectors) cannot sing their parts. As for the first point, one could argue that it is incumbent on the bishop to celebrate the liturgy well, even if it is "private," both for his own edification and those in attendance, and for the glory of God. To excuse the low Mass as being "good enough" for God is just that sort of minimalist attitude to the liturgy/Eucharist that is a problem for Roman Catholics. A "simple" liturgy should nonetheless engage all of man, his senses, intellect, will, and excellences, so that he might glorify God with all of his being.
A vote of no confidence? Beyond that point...