LibreOffice is a perfectly functional spreadsheet for basic spreadsheet tasks. It is, however, not in the same league as Excel for more advanced spreadsheet tasks. Sometimes as a user you just want to be able to use the software that works better, you know?
Yeah, that is the trade-off; if you keep using the proietary software that you're familiar with, you don't have to relearn, but you'll be more dependent on 1 company. But if you spend some time up-front into learning a free software alternative, you won't be dependent on a single company.
But yeah, for some things there are not yet complete free software alternatives, but the gap is really getting small these days. I think for most common use cases for most people, LibreOffice is more than enough. If you need more advanced features that are only available in the propietary variant, try to find ways to not be dependent on that feature, or find an alternative way to do it with free software. If you are creative, there are usually many ways how you can do your work using free software.
But yeah it does take some dedication to this idea. But what you get back is probably, on the long run, gonna be of more benefit to you for the future than if you would invest it in learning the propietary software. Unless you really have a special love for the propietary software company, and you are sure you want to grow more and more into their ecosystem and have no need to have any personal freedom over the software you use.
Yeah, but for retraining to be worth it then in the future your people have to be better or more productive than they would be with Excel and it'll also impact every new hire you make that needs to do the same retraining. Just as good is not good enough. That the tool is free is rarely a strong enough reason especially if there are licenses around already.