Exactly. From my anecdotal chats with friends, they were pretty disappointed with how iOS 11.0 ran. Ars Technica's data backs this conclusion up. iOS 11.0 was a
bad upgrade for "day to day usage" on most iPhones.
If you went iOS 10.3.3 to iOS 11, you were in for a bad time. Notes took 33% longer to open. Safari took 25% longer to open. Mail took 28% longer to open.
Apple has no one but themselves to blame for a below-average iOS 12 uptake. iOS 11 was awarded Apple's "We are proud to stand behind this software" moniker. You--without question--immediately lost a lot of hard-won goodwill, Tim Cook.
It'll take ordinary consumers a significant amount of time to "regain trust", which will happen more by word of mouth than another 'iOS 12 is super fast!" YouTube video.