Present day (this is a more accurate term than "modern") progressives have evolved significantly and would not think so (mainly owing to learning from the mistakes of proponents of eugenics over the last 100 years). That was my point, what was seen as forward thinking 100 years ago does not need to be seen as forward thinking now for the term forward thinking to have utility. It must take into consideration context and many "progressive" people of the past would strike us as troglodytes today but may have been progressive for their era.
But fair enough I was wrong to not pick up on which specific progressive movement you are talking about, to use the hypothetical that the progressive movement of that era was about to adopt eugenics my answer would be that yes, they were progressive for the time. They believed (incorrectly) that eugenics would advance society. Modern day progressives do not believe this and this is not some inconsistency that invalidates the term, it is a natural evolution of political positions more so than even word meanings.
If 1900 is non-modern to you, then "progressive" is not a modern political term. It's a term with a history. But if your point is that the history is irrelevant because people reinvent the meaning of the term ad lib, I suppose that's my point in different words. I rest my case.
That's just a very silly case then (that the word has no meaning because people give it different meanings), there is not a single word in human history that has not suffered from people reinventing the meaning to some degree and is no basis upon which to decide that one particular word is irrelevant.
There has not ever been a central authority for the English language in its history (and even then, in other languages where there have been people used language as they liked and they didn't get to do anything about it), all its words have been open to people reinventing the meaning of the term "ad lib". Bad came to mean good, sick became to mean very good, it just happens. Even if it's not "literal" enough for your arbitrarily selected definition that you claim is the one true definition of the word.
You just cannot claim any authority about what words mean, linguists describe the current state of what people use the word to mean. When lexicographers write dictionaries they don't tell people what they think the word should mean they describe what they see people using the word to mean. Words have no inherent meaning except what people give them. It's all arbitrary, "duck" could just have well have meant "horse" and "horse" meant "duck" if it played out that way. Nothing inherent about the way these letters are ordered dictates what animal they are, this is just meaning lent to these patterns by humans and humans can and will change the meanings even if that does not sit well with you.
The bottom line is that progressive does mean (for the majority of the population) something that you claim it does not, and in this case I am reminded of the old lady exclaiming "look at my young boy! everyone in the parade is marching out of step except my fine young man!"
Language is what it evolves to be, and in this case "progressive" has taken on a useful and clear meaning whether or not you like how "literal" it is according to what you think those letters arranged that way should mean.