You're absolutely correct about speed not being "everything" but rather "decent speed" being a very useful adjunct to successful running in the middle distances and long distances. If speed were really "everything" you would have 1:44.00/800 runners dominating the middle/long distances, which is rarely or not often the case.
Aouita, 1:43.86/800 had one of the best speed bases in his day, and posted other monster times (especially at 1500-3000) of 3:29.46, 3:46.76 (mile), 7:29.45, 8:13.45 (2 miles), 12:58.39, 27:26.11, back around 1987.
El Guerrouj, was an interesting case, being dominant in his day at 1500-3000 distances, but his pb for 800 was "only" 1:47.18 in 1995. This did not stop him from posting extra terrestrial times of 3:26.00, 3:43.13 (mile!), 7:23.08 and 12:50.24.
Mo Farah also had a modest 800 best of 1:48.24 achieved in 2008 when he was 25 years old. Of course, in Farah's case, it could be argued that he did not achieve his true potential until his early 30's when Alberto Salazar revamped his training and lifestyle. Farah's range was also impressive with 3:28.81 (some will argue that the Monaco track is "short"), 7:32.62, 8:07.85 (2 miles), 12:53.11, 26:46.57, 59:32 and 2:05:11 the latter marathon at Chicago when Mo was 35 years old, in 2018. From a style and technique point of view, Mo was always my favourite with his long loping stride and ability to out psyche and out sprint his rivals in Championship 5000-10,000 races.