It is interesting this question focuses on the fifth stage of man, the "justice" with his beard and "round belly." From Shakespeare's description of this stage, there is little that is criticised. Arguably, it is actually the final stage of man that Jaques in this play criticises most bitterly, as it is the final dotage of man that is presented most starkly and shockingly, with the following description:
Last scene of all,
That ends this strange eventful history,
Is second childishness and mere oblivion,
Sans teeth, sans eyes, sans taste, sans everything.
This is far more critical than the presentation of the justice, "Full of wise saws and modern instances." The final stage of man returns the cycle of man full circle to the first stage of "second childishness" and then presents an incredibly tragic picture of "mere oblivion," with the repetition of the word "sans" to emphasise how, as you get older, you lose every sense and faculty that you had in life. The final line is of course cumulative in its impact, as it finally reaches the phrase "sans everything." Not only does man lose teeth, sight and taste, he loses "everything" before he dies. This is a tragic, bitter and serious note in a comedy that is characterised by gender confusion and other, more frivolous aspects. Shakespeare seems to use Jaques as to remind the audience of the more serious elements of life that cannot be simply put off by running away to the Forest of Arden.