No, that's not what I'm saying. I'm saying that when you read a line in a silly way that makes the possible impossible, and use that to say that an action simply cannot be performed by the player that otherwise should be possible, then yes, it's railroading. What people are somehow not getting is that this is a roleplaying game. If I say, "My father is lactose intolerant, so he can't drink milk, because dairy gives him gas," no person in their right mind is going to interpret that there is a magical barrier in front of his mouth that prevents dairy from touching his lips, else the universe tears in two as milk entering his mouth creates a spacetime paradox because it has been stated that he cannot drink milk.
If you actually apply the proper use of language, you'd know what the sentence is saying, but it appears common sense is no longer applicable in reading. Even with the Sage Advice clarifying the proper interpretation is that nothing in the game system prevents it, people still don't want to accept that, because they refuse to use basic reasoning.
Saying "you can't use heavy armor because you lack the martial training to use it" does not mean you can never wear metal armor. It means that if you wear it, you gain no benefits of its use, or suffer the game system's proficiency/encumbrance penalties, because you lack the martial training to use it. Same with saying "you can't wear metal armor because you'll lose your magic while you do." The Druid can still put on the metal armor if they say they'll do so, they'll just suffer the consequence of losing their magic while they do, plus any other penalties based on the edition (none in 5E because they are proficient in its use). Suffering the consequences is their choice to make, just as with making any other decision.
The rules say that a character not proficient in the use of tools cannot use those tools. This does not mean that the character is literally physically incapable of trying to use the smith's tools or a poisoner's kit if they're not proficient. There's no magical barrier preventing them from putting their hands onto the tools. It just means that nothing will come of their efforts to use them, because they can't perform the tasks that are listed in the rules as requiring proficiency.
If a Druid says "I put on the glove", you as a DM are railroading them if you say "No you don't." It's their choice to make, and nothing in the game system prevents them from taking the action. If the game system has penalties for it then they can deal with the consequences of their action. It's not railroading to say, "Okay, you put on the glove, but you are now wearing metal armor, so as per the rules you lose access to your magic." It is railroading to say, "Nuh-uh. No you don't."
This is not a video game. You don't get a red X over your character if you try to equip something you're not proficient in. I don't see Paladins getting DM blocked if they want to break their oaths; they're fully allowed to do so, it just so happens that most of the game systems put in penalties for when they do. Such penalties no longer exist for Druids. If they choose to put it on, there is nothing in the game system stopping it, or penalizing it. If it doesn't have penalties in the game system, and you create some, those are house rules.
Sure, that's true, if you ignore the line after it that says "Well, not actually." and then goes on to explain that nothing happens, and that the Druid does not lack the ability to do so.
Or, more logically, if it's universal that Druids suffer a loss of magic for 24 hours if they wear metal, then anyone that captures a Druid and wishes to hold it prisoner, will be able to lock metal armor onto it so they can't use their magic to escape. Never heard the story of the man in the iron mask? Same concept. I could only hope that the DM would have an ounce of sense and doesn't make the game end because the universe tears itself in half when the enemy puts a metal mask on the Druid.