I see two errors here.

Defining technology to be "that thing which makes people's lives better" feels weak, even disingenuous, because trivially nuclear missiles and weaponised smallpox are technologies that fail your test.

Therefore, there exist technologies that can make peoples' lives worse.

The second issue is with your subjective "(people's lives getting better) doesn't appear to be slowing down to me". It's a view you're entitled to hold of course. Maybe you are not aware of other perspectives. It may have escaped your notice that in the last decade digital technologies have substantially changed in their nature. They've been at the centre of scandals over the erosion of democratic values, decline in education, attention disorders, social fragmentation, childhood depression, pollution and e-waste, conflict minerals, energy consumption, loss of privacy, dignity and rights... Must I go on?

To hold the idea that "all technologies naturally improve human life" by definition alone seems like a desperate escape from the facts.