Are you religious?
You do seem to be implying that mutations prevent organisms from doing/being/functioning as they are 'supposed to'. But to make such a weird authority claim, you imply that [by some mysterious authority] there are such things as 'perfect' kinds.
How on earth did you come to this conclusion? Where is your evidence that 'perfect kinds' ever existed? Do you happen to have discovered or chanced upon a fossil of a perfect kind? By what yardstick do you measure perfection?
I draw this conclusion from the fact that you state that all mutations are 'deleterious', i.e. evolution is a process of degradation from a supposed 'higher form', supposedly, therefore, going backwards in time, each 'kind' becomes more 'perfect', and we eventually arrive at some kind of utopia [unless you deny that any mutations occur].
Also, even if your 'theory' is correct, how does the supposed damaging nature of mutations prevent the creation of new species? degradation might be faster in some sectors of a population, hence producing a lower and less 'perfect' [but different nonetheless] species.