I'm of the opinion that many people think that rising sea levels is a phenomenon that has only occurred since they were born.
You are missing the point of the thread. It does not matter of sea levels are constantly changing or it is only just now taht people are starting to worry about it (which makes sense as it is only in the last 100 years that accurate records have been kept). The why and when are largely irrelevant.
The point of the thread is "Is anyone worried about it" and the answer is "Yes, there is a reasonable percentage of the population that would consider being close to sea level in the purchase of any land as a negative."
That's why it is a big deal to people who own property at or near sea level.