It depends what you mean by the term 'speedster'.
If you're asking whether Wonder Woman has superhuman speed or not, the answer is a definite "yes". The DCEU version of Diana clearly shows it in your video clip, and the comicbook versions of her have been stated and shown to have it on multiple occasions.
The original, early Pre-Crisis / Earth-Two version of Wonder Woman was stated to possess "the speed of Mercury" in her very first appearance in All-Star Comics #8. This was stated again in the first issue of her solo series, Wonder Woman Vol 1 #1.
The later Pre-Crisis / Earth-One Wonder Woman actually bested Mercury in a footrace, in DC Comics Presents Vol 1 #41.
The Post-Crisis / New Earth version of Wonder Woman was granted speed and flight by Hermes, as part of her origin story in Wonder Woman Vol 2 #1, and was stated to possess "superhuman speed and reflexes" in Who's Who: The Definitive Directory of the DC Universe #26.
And the current, Rebirth / Prime Earth version of Wonder Woman was ranked in seventh place among DC fastest characters (ahead of Godspeed, Shazam, and Kid Flash (Wallace West)), in DC Nation Vol 2 #2.
If, however, you're asking whether Wonder Woman is in the same league as the Barry Allen or Wally West Flashes in speed, or whether she's as adept at using her speed as they are, then the answer is a definite "no".
In JLA #43, Wonder Woman challenged the Flash (Wally West) to a friendly race, and it was shown that he could stay ahead of her while running backwards.
In JLA Classified #17, Wonder Woman noted that although she was "very, very fast" compared to a normal mortal, the Flash (Wally West) was an "indistinct blur" compared to her.
And in Wonder Woman Plus Jesse Quick #1, Jesse Quick noted that although Wonder Woman possessed the speed of Hermes, she lacked "the skill of someone for whom speed was their weapon".
In regard to Wonder Woman's speed not being focused on in Justice League (2017), it's much the same in the comics, and it applies to Superman as well. Those characters who possess super-speed as one facet of a broader power set (i.e. Superman and Wonder Woman) tend not to use it as consistently as those who rely on it as the sole weapon in their arsenal (i.e. Flash or Quicksilver).
I think comicbook writers make the same calculation you have -- that if beings as strong as Superman or Wonder Woman were to use their super-speed constantly, they'd be damn near unstoppable -- and consequently, they just don't write them as using their speed constantly, or even that frequently. And if you're looking for an in-universe explanation for that, none has been given to the best of my knowledge.
I recall a Marvel Comics editor, Tom Brevoort, being asked a question along these lines in relation to the Marvel Superman knock-off, Gladiator, and he described it as just a "conceit" of the medium that such characters don't use their super-speed as efficiently as they could on paper.