This is such a weird line of assertion that I wonder if you'd apply it in any other context.
The problem doesn't just exist for dedicated Parler die-hards. The problem exists for Parler trying to become a compelling platform at all among everyone else. And that problem exists for all Parler users including all the would-be users and all people trying to develop a following on Parler.
> Oh no we have to go to a bookmark in a browser instead of having an app or even an icon on a homepage
Sure, not a problem for Parler die-hards. Massive shortcoming for everyone else. iOS users can't even receive notifications from a website. Parler's target audience isn't just the people willing to jump through hoops. If you're someone trying to create content on Parler, your target audience isn't just people willing to remember to check their mobile browser every once in a while when every other app (incl Twitter) gives them real notifications.
You're saying that these obstacles either don't matter or they're inconsequential as long as your product is good, and you're sorely mistaken. You don't want to be lacking a notification system as a fledgling social media platform. Just consider how every time someone receives a "X replied to you" notification and returns to the app, how that enriches the entire platform.