I haven't unlocked the marketplace yet so I've just been going there occasionally to plan out my home. Because you can swap through all of the variations, it helps me see what would look good without me wasting customizing boxes on it.
Back on my old island pre-HHP I would go to Photopia ALL THE TIME to design rooms, but after getting HHP I just kinda. Stopped. And I haven't visited yet on my curent island because I forget what you have to do to unlock the shops.
I'll say sometimes. I am trying to get art from Redd there but I also forget some days or just don't care enough to go. I use Cyrus a fair bit since my catalog is far from complete. The other thing I mainly use Harv's for is trying clothes on my villagers before I gift it to them because I gotta make sure they look good.
I still visit Harv's Island, yes. There are still some clothing items that I still need to fill up my catalogue, especially shoes, socks, and accessories like purses and bags, so I like to see what Kicks has in stock each week. I like to see what Saharah has in stock as well. I'll occasionally need to go see Cyrus to get some furniture items customized and thus fill my catalogue up some more with all the various colors and styles. I also like to get my fortune told by Katrina in the hopes of getting her special items, though I don't do that as often anymore since I have them now.
I voted sometimes, I don't go there all the time cuz i'm usually too lazy, but sometimes i'll remember that I still need some items from redd, or leif and i'll go see what they have there, or I need to customize something with cyrus and i'll just pop in for a quick moment. Oftentimes I usually go when I'm about to play the dlc, since im already at the airport you can go to harv's island and then theres an option to go straight to work from there, so idk to me it feels like less jumping around.
I go at least once a week to see what Saharah, Kicks and Redd are selling, sometimes twice if one of them is visiting my island on Monday.
I’ll go more often if I want to take fun photos with my villagers, try out room designs, design something for a TBT event or invite a new villager to unlock their poster in my catalog, but 1-2 visits a week are usually the max for me.