In my experience this can be pretty individual based on the person, since some people will consistently have luck with plants that are considered difficult, while they might struggle to keep more basic plants like pothos alive. I think generally, the plants people regret buying the most are ones they might just not have the setup for, such as tropical plants that are going to require tons of light and humidity if someone lives in an apartment for instance without much natural light. I do tend to see people regretting plants like birds of paradise or monstera, where when cared for properly, these plants can easily grow many feet tall and end up becoming difficult to move or may even outgrow your home altogether. I tend to like things like ferns and palms as good alternatives to giant plants like these, since they are relatively slow-growing and won't tend to get so tall you won't know what to do with them.
I've found in houseplant circles that lots of people regret buying rubber figs or rubber trees. These are gorgeous and very popular houseplants, especially for people looking for a bigger indoor plant. But, they can be exceptionally particular about light and water requirements, and I think lots of people find it difficult to find that sweet spot in care where these plants will truly thrive. So, you tend to see lots of rubber trees online that are dying and their caretakers have no idea why. I think parlor palms can make good alternatives for rubber figs. While they do have a different look, they tend to be much lower maintenance in my experience, and more adaptable to a range of conditions.
In my time running a small plant shop, I’ve noticed quite a few customers come back struggling with fiddle leaf figs. They’re beautiful, sure, but they're pretty finicky about light and water, which makes them a headache for folks who haven’t mastered the balancing act. They don’t do too well if neglected or if you go the other way and overcare for them. A solid alternative would be the snake plant. It's practically bulletproof, thriving on neglect, and looks fantastic in any corner. If you want something with a bit more drama but not as touchy as the fiddle leaf, a rubber plant could be your go-to. Both are forgiving and handle a range of lighting conditions much better. Trust me, sometimes the less fussy plants are the real show-stoppers in your space. Give 'em a try, and you'll see how stress-free plant parenting can be!