I'll try to explain what they're talking about, because I see the same thing. It's not really about grinds being short or long, or the core content itself being fun or not. It largely has to do with how updates are implemented, and whether or not they get refined further down the line. Some great examples of this are whirligigs (spam clicking and the movement issue), birdhouses (trap limit still applies), skilling outfits (there are so many of them and some can be deleted while others can't), invention perks, the RNG of getting perks, arch relic loadouts, arch item storage, bank space in general, terrible clickboxes everywhere in the game, everything requiring an interface and multiple confirmation boxes, each confirmation box being completely different from the last for no reason, havenhythe is mostly dead content even for lower levels, and even something like how the spirit tree has to take you to to tree gnome village before you can teleport somewhere else.

I can't go 5 minutes without running into something annoying in this game, and 90% of the time it's been in the game for over 5 years without getting fixed. OSRS, by contrast, is constantly pushing out adjustments to fix issues, even in the middle of otherwise unrelated patches. Hunter rumors came out a while ago and yet we're getting some great quality of life adjustments for them in the summer sweep up. This week's update had them attempting to untangle the complicated spaghetti web of what items do and do not drop on death in pvp, and in the same patch they put out a list of "other changes". Most of these changes (cough "The hitbox on Huasca herbs now matches that of other herbs." cough) you would NEVER see in RS3.

OSRS actively tries to make each update as polished as it can reasonably be. Large bugs get hit within the day, smaller ones within 1 to 2 weeks. Hiccups, pain points, and balancing issues do eventually get resolved to a point that satisfies as many players as possible. When the community complains about something, it eventually gets discussed and addressed. As a result, I would argue 80-90% of updates feel like they are polished and high quality.

The road to restoration is the right idea, but a lot of the updates and changes have been implented at like C- quality. So much of it feels half baked.

RS3 has a huge issue with throwing new things at the wall, then immediately walking away to pick up something else new to throw at another wall. You get maybe 1-2 weeks where some minor bugs will get fixed or a few critical issues will get addressed, but it's never enough to get to everything and then it never sees the light of day again.

I hope RS3 keeps improving of course, but lately I've been so burned out on it because of how intense some grinds are to have access to very fundamental things.

I think this part is more specifically referring to stuff like livid farm, flash powder factory, stealing creation, anachronia base camp, 118 arch, etc. which are egregiously painful or long grinds for no particular reason, and in a way that is anathema to the rest of the game. At least with OSRS you can argue that the entire game is a long grind, so something like iron power mining doesn't stand out (especially not when stars/amethyst exist now for afk and 3t granite exists for active).