Is this your way of saying that yes, you would complain loudly about any of the changes I mentioned, but you don't think others should because your reasons are better? In which case, you appear to have missed all of my points.
"Power user" is not a well-defined term and it can mean almost anything, including people who have absolutely no clue what they're doing. Let's take a more specific example. I know one of those people who is a big Excel user. He probably should have been taught real programming, but nobody did it. Instead, he self-taught a lot of programming concepts in Excel. I know the image you have, because I tend to have the same one: someone who thinks they're an expert programmer because they've managed to have ten formulas in the same sheet without any compilation loops. That's not what this guy is like. If you want complex mathematical models performed, he can probably find a way to make Excel do it faster than a programmer will, mostly because the programmer will need to spend more time on data import than he will. He has been using Excel for decades, and although the things he makes are less efficient and less maintainable than an actual program, they do work well.
If you tell him he has to use LibreOffice Calc instead, he will react much like if you went to a Cobol programmer and told them that they will now be using Java for everything and to start converting. He doesn't know how to use LibreOffice, and some things won't work, and because these are spreadsheets, there's far less automated testing, so he's going to have to manually check everything to verify that they didn't break. Let's see how to handle this and what happens if you, the IT team in charge of the transition, try them:
1. Fire that guy, replace him with someone who knows LibreOffice: his team freaks out because there aren't too many people listing LibreOffice as skills and they're the people who would have to find the replacement. They join ranks to fight you.
2. Fire that guy, replace him with a programmer: Again, the team freaks out because although they aren't as good at Excel as that guy, they can use it, but they don't know how to program so making changes will be challenging. Also, they're going to have to explain lots of details about their processes to someone who has a completely different background and they're worried it will go badly.
3. Provide training to help him and them learn how to use LibreOffice. They grumble, but if the training works, they will be able to convert.
4. Buy an Excel license and stick it in a Windows VM (if you're also switching to Linux) and let them keep using Excel. They're mostly happy.
5. Hire a programming team which you can divert among the various teams writing programs, have the spreadsheet users work with them to reimplement everything as a program, then either move the Excel guy onto the programming team if he learns how to code, have him focus on more business-focused things when his spreadsheets are obsoleted, or make him redundant when nothing he does is necessary because it's been replaced. The outcomes are very positive, but doing it properly takes a lot of time and money.
When comparing these options, the best outcomes tend to come with choices 3 to 5, but choice 5 is so hard that it's usually not an easily chosen option. Choice 3 means you have the least disruption, and choice 4 means you have the least financial cost because intensive retraining in LibreOffice, the kind that shows you how to accomplish those things you did in VBA, is more expensive than just giving that guy an Excel license. You have instead chosen the first two options whose primary advantage is that there's less work for the IT department because all of the disruption is the responsibility of the team with the spreadsheets who has to find new people and get them trained. This is why, unless you are an all-powerful leader who can do whatever you want on command, you will have more trouble choosing those options. If you can't even recognize why this is the case, then the people who make the decisions are all too likely to choose option 6: ignore the change request from the IT guys and buy some more licenses from Microsoft. If you want them to choose something other than option 6, you should start realizing why that "power user" is still employed there and why you can't ignore them the way you want to.