I am very happy with mine and have only ever had one hiccup during updating that was due to my Dockerfile removing one dependency to many. I've run it bare metal (apache, mariadb) as well as containerized (derived custom image, traefik, mariadb). Both were okay in speed after applying all steps from the documentation.
Having the database on your fastest drive is definitely very important. Whenever I look at htop while making big copies or moves, it's always mariadb that's shuffling stuff around.
In my opinion there are 2 things that make nextcloud (appear) slow:
Managing the ton of metadata in the db that is used by nextcloud to provide the enhanced functionality
It is/was a webpage rendered mostly on the server.
The first issue is hard to tackle, because it is intrinsic and also has different optimums for different deployment scales. Optimizing databases is beyond my skillset and therefore I stick to the recommendations.
The second issue is slowly being worked around, because many applications on nextcloud now resemble SPAs, that are highly interactive and are rendered by your browser. That reduces page reloads and makes it feel more smooth.
All that said, I barely use the webinterface, because I rarely use the collaboration features. If I have to create a share I usually do that on the app because that's where I send the link to people. Most of my usecase is just syncing files, calendars and contacts.