Gentrification is a "dysphemism" (opposite of euphemism). It's basically a buzzword made up to give a negative connotation to something that isn't inherently negative.

People move around. Some cities grow, others shrink. New jobs get created, old jobs disappear. Some housing gets more expensive, some housing gets cheaper. Some cities get wealthier, others get poorer.

We'd still be living in caves if our goal was to forever keep all cities and towns the exact same way they've always been. Which is basically the goal when people criticize "gentrification".

Gentrification is an overblown concern. No one has the right to live in a specific area. Migration is human tendency. Just like poor people have a right to move from a rural area to a city in search of better employment opportunities, people with money have right to move to cheaper locations to get a better bang for their buck.

There's nothing overblown about being forced out of a neighborhood you've lived in all of your life. Now the problem is reaching epic proportions all over the world.

I also do not understand how the second sentence and the last aren't a direct contradiction of each other.

The bigger complaint looks like it's about buying houses as investment vehicles, often leaving them empty, rather than using them as housing.

Not so when it involves crossing country lines.

A country should focus on its citizens first, foreigners second.

Then again EU is an unique experiment as it is.

Yes and No. I described gentrification. No, I did not participate in it because I received a Portuguese salary from the start. I'm working at university where the salary levels are fixed by state institutions. (Which is a huge problem if you want to attract senior researchers from abroad, and also a problem because it causes talented people to emigrate.) The reason why I paid a rent that was then higher than usual was because landlords in Portugal assume foreigners are wealthier and therefore it was very hard as a foreigner to get an apartment at the low pricing that my Portuguese colleagues were paying.