Well made furniture can be pretty difficult to make. I'd guess for the average skilled person it probably takes a half dozen projects and lots of research before you start making pretty decent furniture, so keep that in mind!

On top of that, designing good looking furniture takes much more skill and time. Sometimes ya just don't have the knack either.

That being said, it's still super satisfying to make furniture, even if it gets cracks from expansion, has all kinds of weird defects, or doesn't look all that great!

Not necessarily in ways that matter. If I use equivalent materials (MDF), it's still more expensive for me. If I use good plywood (which is usually the right choice) or solid wood (which despite common perception is the wrong choice for almost anything involving large flat panels), it may be more durable but becomes significantly more expensive.

IKEA stuff may not last centuries, but it often lasts fine for its intended use. I have a number of cheap IKEA Kallax-style bookshelves around my house. They're made of cardboard, hopes, and dreams, but have held up to all the loads I've thrown at them for years and even survived a couple of apartment/house moves (admittedly, the big one would probably not survive another move). How many people ACTUALLY want to keep the same piece of furniture with the same dimensions and styling forever? How many people who want to actually manage to in the face of new residences, combining furniture with roommates/partners, etc.?

IKEA is only one example. The same arguments apply for other brands, including some "real" furniture. I'm in the middle of building a queen-sized Murphy Bed. All said and done, my material costs are approaching $2000 (without a mattress) and I've spent several weeks worth of evenings on it. It's been a challenging project, and I don't regret it, but economically it would ABSOLUTELY have been better to buy one.

> is the wrong choice for almost anything involving large flat panels

This is not at all a common or majority opinion among the fine woodworking community. There certainly are advantages to engineered wood products, but the shortcomings of wood as an organic material (it moves with respect to humidity, regardless of what you coat it with) can be overcome through successful furniture design.

Also, IKEA is not the comparison for my DIY projects. I compare quite favorably in cost to Thomas Moser, West Elm, etc.

It's difficult to generalize, given that they have an absolutely huge inventory, but the IKEA pieces I own (Two tables, two sets of cabinets) have held up for a decade, and are likely to hold up for at least two more.

The key to IKEA furniture, I have found, is to place it where you want it and never move it. I have Billy bookcases that have lasted 15 years while being FULLY loaded. I also have had to replace my son's Billy cases as we've rearranged and updated his bedroom multiple times over the years. He doesn't abuse them, they just don't like be moved in and out the room,even empty, for painting or other projects.

Wood's expensive. High quality exotic wood can be very expensive. Someone making their first pieces of furniture will likely (should) be using MDF or pine, same as an Ikea item, but will still be paying more just for the materials than the finished item.