I know folks used to say that Common Lisp was too big, comparing it to C or Pascal. But is it really big compared to, e.g., Python, JavaScript or Ruby? If anything, a common complaint now is that too little is standardised (which is true, but good portable libraries exist for most such things).
And, as lispm notes, one can implement a subset of Common Lisp—all that's required is that one define the subset.
Interestingly, so far people preferred to implement dialects of Lisp-1 mostly. Not that many Common Lisp subsets or even Common Lisp-inspired languages around. I can only name Shen as one obvious exception from this rule.
And, as lispm notes, one can implement a subset of Common Lisp—all that's required is that one define the subset.