In Bacon's time, common law countries had a greater proportion of legal rules articulated in case law precedents, and a small proportion of legal rules articulated in statutes passed by the legislature than it does today.
Further, meaningful access to case law resources for litigants was much more difficult in Bacon's time than it is today. There were fewer secondary sources, few of those were comprehensive and organized at the top level by subject matter, you couldn't do word searches or key note searches, and even primary sources, consisting of statute books and case reporters, were limited in number, expensive, and hard to use.
The private sector working together with civil society institutions would subsequently produce in American law, the digests and the "restatements" of the common law rules that Bacon sought (neither of which are themselves binding precedent).
Characterizing the distinction as between a "rule based" system and a "formless" one is in my opinion not a description that furthers understanding. In many respects, the common law of Bacon's era has more black and white "rules of law" that could be applied umpire-like by judges arising out of an already substantial collection of case law precedents, than civil law countries whose statutory laws often stated "standards" that set for vague general principles without little guidance regarding how they are applied in particular circumstances (as opposed to more specific and unambiguous "rules"). Precedents provided clear guidance in common law systems in a lot of specific fact patterns (e.g. the working of the "mailbox rule" for contact formation), but civil codes lacked the same level of nitty gritty detail. In Europe, in contrast, lawyers had whatever late Roman Empire legal digests had considered, in summary form, but there was no elaboration or development of this in fact patterns present at the time the court was making decisions but not in Roman times.
The Napoleonic Code and other major civil codes of Continental Europe hadn't been drafted at the time that Bacon lived. But what it did have what a subject-matter organized digest of the holdings of legal cases decided in the Roman Empire during Emperor Justinian's reign which were functionally treated as binding statutory authorities by the Latin speaking educated elite starting in the Renaissance and "early modern" period in European history which is known in legal circles as the process of the "reception" of Roman law after it had been dormant for centuries, a process that Britain did not participate in itself.
The issue was not that the common law system of Bacon's time lacked legal rules, or that it was formless in the sense that there was not a clear, albeit, somewhat latent structure to those rules, although few people had access to the whole of the relevant authorities.
Instead, what was missing in Bacon's time was a compact, comprehensive, statute-like, widely available authoritative statement of private law (the law governing the interaction of non-governmental parties) and criminal law, that could fit easily in a hefty volume or three (written in Latin) on a library bookshelf.
This meant, in practice, in common law systems, that it was much harder to deal with legal questions (both transactional and litigation issues) without the assistance of a highly trained specialist lawyer who had spent years learning the system, while in civil law countries, an educated individual who was literate in Latin without other formal legal training had much more of a fighting chance of figuring out what the law required and said, reducing (but not eliminating by any means) the benefits associated with having highly trained legal counsel.