BuyFromEU

It depends on what you want to do. If you're a business and need those advanced Excel features, those plugins for your ERP and CRM and your job is to create Powerpoints, then Libre Office will give you a lot of pain. If you're just some private person who wants to write a letter every few months, is maybe doing some light spreadsheeting to split the costs of a vacation and the only presentation you created was that one for uncle Ralphs birthday last year, Libre Office is totally ok. There really is no reason to pay for MS Office

If you change the UI to the newer Tabbed Style it's a decent replacement. Still inferior in many points, but perfectly usable

In a vacuum, it would be a decent replacement.
In fact, MS Office 365 is getting worse every month.
However, the world still can't seem to stop sucking Microsoft's cock.

So, to turn in an assignment in university, it has to be done in Microsoft Office.
Maybe if you write it in another program, the anti-plagiarism software will accept it, but you don't know that in advance.
And if it doesn't, your assignment counts as not turned in on time.

And in business, the old saying "no one ever got fired for buying IBM" still holds true.
Other solutions exist, but if the head of the IT department pitches ditching Microsoft, and the project fails, they risk their job.
While simply telling the C-Suite "This is how much licensing costs per year" is the safe option.

A few weeks ago I asked for a free alternative to MS-Office and Onlyoffice was recommended to me more than Libreoffoce. .

It's ok. A bit of a learning curve to get the best settings for your needs, but its doable. To get rid of microsofts office suite its definitely an option.

The different styles are great to try out.

It will likely be a question of what you're used to and what specifically you use it for more than anything else. IMO, it's dramatically better than office 365.