I think it may be more that the content is getting stale too quickly. Like place once and done.
Over watch gameplay and especially movement is largely the issue here.
A lot of players feel forced to play the meta. Then a few don't, and the meta changes.
To compete at anything means making the decisions that put a contestant in the best position to win. A "meta" is the most optimal team composition for a given map. To play off meta is uncompetitive.
> Then a few don't, and the meta changes.
This is not how metas change.
At the time, teams were running Hammond/Sigma/Tracer/Echo mostly. Depending on the map, Rush (Rein/Dva/Mei/McCree/Lucio) was also viable. After the change in the patch you referenced, Hammond was no longer optimal so Sigma/Ball stopped being played in favor of almost fulltime Rush.
More recently Double Bubble has become popular (Zarya/Winston), but Rush is still played a ton and the dominant meta.
The patch notes for that patch can be found here: https://us.forums.blizzard.com/en/overwatch/t/overwatch-reta...
Fortnite can afford to keep artists and programmers on staff to develop a huge amount of content because they have consistent money coming in. This isn't the case for OW and I hypothesize this is why they struggled to crank out new content.