I learned during my long-ago university days of the key historical change from 'status' to 'contract'. In a sense, modern civilisation began when, not only were rulers subject to the law, but your legal obligations depended not on who you were but what you had agreed.
No more jus primae noctis or knight service. Your obligations depended upon the contracts you entered into. Moderns might think themselves 'wage slaves' because of a real or perceived lack of job opportunities, but their employer had no claims over them qua employer, only by reference to their contract of employment. Their serfdom was therefore metaphorical at most.
As recently as the 1970s then, this was seen as progress in itself and as a key enabler of progress. It was a thoroughly civilised way of organising human relations. Modern society was not possible without it. Indeed my legal history lecturer (leftist though he was) presented it as a key enabling factor of the industrial revolution and therefore of all modern prosperity.
Yet the drift back to status was already well underway. English law, for example, limited an employer's response to the breach of contract involved in refusing to work if it was in the context of a protected strike lawfully organised by a trade union. The status of being under the protection of a trade union (a modern descendant of a medieval guild) alters your employer's legal rights and - in a certain sense - justifies your breach of contract.
For a long time the police operated with the same power of arrest as any other citizen. If someone commited a felony (now an 'arrestable offence') you or I could arrest them and so could a copper. The only difference was that he was paid, trained and expected to do it. I always thought that was a wonderful check and balance on police power. It's a dangerous thing to have a professional police force because, among the honest decent people attracted to such work, there is bound to be a higher-than-average proportion of thugs and bullies. Bossing people around attracts bossy people.
Now the status of being a police officer or enjoying one of a large number of other state-granted statuses, confers special powers of arrest, search, seizure and forced entry. Even, as we have seen in recent days, forced entry to a mother's womb.
Landlord and tenant law tends to assume (ridiculously in the modern era when he might be Google or Microsoft and his landlord might be your mother's pension fund) that a tenant is a weaker party entitled to special protection by virtue of his status.
Similarly consumer legislation operates on the basis of a cartoon caricature of a buyer like Wile E Coyote; endlessly supplied with disappointingly non-lethal-to-road-runners goods by ACME.
The Unfair Contract Terms Act 1977 specifically prevents people from entering into, or at least from being bound by, contractual obligations, based on their status as 'a person dealing as a consumer.'
The notion of 'positive discrimination' confers for the first time in law an actual right to be racist (if you ignore, as I do with utter contempt, the socialist claptrap about racism being by definition a problem exclusive to white people).
The concept of 'hate crime' makes it more serious to insult, hurt or kill people enjoying a specially protected status. Current law thinks some deaths diminish me more than others. I disrespectfully disagree.
Your status as a citizen imposes all kinds of obligations on you. For example you must surrender a percentage of your earnings to the state, pay your local council for the privilege of living in your own home and hand over 45% of your parents' wealth above a certain value on inheritance.
It would be amusing if it were not so sad that modern 'progressives' have for decades been busily restoring a key concept of feudalism and systematically undermining a key legal foundation of post-feudal prosperity. Their labels may not openly be 'lord' and 'vassal' but their world view is founded just as much on different rights and duties for different classes of human.