Sometimes I think it is easy for people to be get a negative opinion of Liszt, because, yes, it is undeniable that he wrote a lot of flashy trash. I think that aspect of his music has to be put in the context of his life and times - he was of course a virtuoso performer and as such it was expected that he would produce and perform crowd-pleasing music. Almost all the virtuosi of his time did likewise. If you read letters he wrote, I think it is obvious he was acutely aware of the incongruity of these pieces with his desire to be taken seriously as a composer.
Now, if he had not had a career as a virtuoso, aided by the more frivolous music he wrote, he would not have amassed so much wealth, would not have been able to fund Wagner and help countless young musicians, would probably not have been able to give free masterclasses at Weimar, etc. So, I think, we should not read too much into a lot of his earlier music, as in ihis later life, he did the above things for the good of music, which were perhaps a subconscious part-atonement for the musical sins he knew he had committed earlier on.
Of course, there is no reason why anyone should choose to like Liszt's music, but I think it would be wrong to dismiss him on the basis of some of his more lightweight music.