I don't accept that I am a "polluter". Nor do I believe that I am obliged to accept your opinion as the the correct range of use cases.
"Railroading" is a normative notion, in the sense that in many cases of its use (perhaps not all), it is used to describe something as not meeting some sort of implicit standard. The standard, in the context of RPGing, is sufficiency of player participation in establishing the shared fiction. When you call something a railroad you are pointing to a concern about such things. Likewise in my case.
I draw the line of the standard differently from you. I know that. You know that. There is nothing objectionable about me stating my point knowing that you don't share my judgement. I don't see why I am obliged to abandon my normative threshold in favour of yours.
There is ZERO difference in this respected between "is a railroad", "is artificial", "is an obstacle to immersion", etc.
I don't get offended by learning what was already obvious to me, that some people's standard for artificiality in RPGing is different from mine. I don't see why others should get offended - that's a strong word! - by learning what was already surely obvious to them, that my standard for sufficiency of player participation in establishing the shared fiction is different from theirs.
I feel like we are actually making progress here! It seem like you accept I might have a basic understanding of your position, and I start sensing an outline on how you can have arrived at "railroading" as a suitable word for the concept you try to express.
The key issue here is your "The standard, in the context of RPGing, is sufficiency of player participation in establishing the shared fiction.". If this had indeed been the universally accepted standard for the use of the word "railroading", your use of the word would indeed have been fully unproblematic as you point out in your last sentence.
However, the issue is that this is not the commonly accepted standard. The common standard for calling something "railroading" is the degenerate case where it is not only absence of subjectively
sufficient player participation, but actually
no player participation. The normative weight of the term lie in that it is assumed that this level of participation is not
sufficient for anyone. Moreover the most common use of the term is in a context where a GM is accused for providing
no opportunity player participation trough either incompetence or intent. This is why people might be prone to be offended if you are labeling their activity as "railroad" without further explanation. They can reasonably interpret your statement as a claim that they are either incompetent or having bad intent. I guess you don't fail to see how anyone can be offended by feeling they are wrongfully accused of being incompetent or having bad intention?
Talking about level of player participation you prefer is a valid and interesting topic. It can be critical for finding a group that aligns in what you would like to play, and should at the very least be a part of session zero. As such there are standard patterns to talk about what level of player participation one prefers. In this context i have seen railroading used as a term to describe the
direction of less player participation. However in this context where there indeed are talk about degrees of player participation the "railroadiness" is not having the same normative meaning. In this context I think I have seen as many people stating a preference for less degree of player participation (being guided, experiencing something prepared, railroady at times), as people requesting higher levels of player participation. However in this context also the terminology use is generally indicating a preference "closer" to railroading (denoting an axis toward an extreme). The word "railroading" itself appear understood to be the degenerate case of
no player participation at all.
There also is a lively debate about what is railroading, but that generally revolves around identifying cases where there can be considered
no real participation. The underlying motivation for this debate appear to be to determine what is the scope of what is considered universally bad and should be avoided in general. This is where concepts like quantum ogres and multiple doors with no information tend to be central. The way you are writing about railroading is also very easy to interpret into this context - in which you are misunderstood to claim that even sandboxes are to be understood as not providing any real player participation, and hence
universaly bad.
The best way I have managed to read you now is the following: You are aligning with the railroading term as commonly used in general under the understanding that there is still
no player participation
of a particular kind - which you further describe. Moreover you appear interested in preserving a certain norminative weight to the term. However this norminative weight is supposed to be taken as a purely subjective one, as opposed to the more objective one most usage of the word is normally associated with.
As such you are appearing to do two controversial things with the word "railroading", the first, most obvious, and in my eyes quite reasonable is proposing a new way to gauge if player participation really "matter" with regard to what happen in the game. I think the observation that for many what is important isn't the range of options a GM provide, and the range of possible consequences the GM envisions as possible that is of (most) importance for a player feeling that they really contribute, but rather the extent the player's original contributions make a (lasting/important) impact on the fiction.
However the second thing you are trying to do with the word is to reject the proposed
objective normative weight of the term - replacing it with a purely subjective weigth. You appear to be either oblivious to this objective normative sense of the word, or actively ignoring it. This is the property of the proposed understanding of the word "railroad" I find most controversial, and the reason I think such a change in use simply cannot fly. I think we as a community still need a term to describe this universally recognized problematic state of game
that there is a steady stream of horror stories confirming exist in the wild. Railroading is the word we have used for it, and as such I don't think it can be repurposed the way you suggest.
In light of the above I still strongly advice you to figure out a new word. If you want the word to still carry a subjective normative weight, I agree that simply
sightseeing might not fit the bill. Maybe "just sightseeing" might be conveying both the feeling of not being able to creatively contribute, while also conveying the personal preference that you yourself would have liked more?