Its only ecologically sound if you throw away your heirloom furniture after 10 years just like you have to throw away the IKEA furniture. If you still use the same table your great-great grandma used the heirloom furniture is better ecologically.
Considering the amount of glues and plastic required to make IKEA furniture I'm not convinced even at the 10 year mark IKEA is better ecologically, but that is a complex question that I wouldn't know how to analyse (if anyone tries I expect a few years latter someone will find a significant factor they didn't account for, and again a few years latter...)
Arguably, hiring a moving truck just to ship my grandmother's dining table across the country every 2-3 years is less ecologically sound than buying a flatpack from Ikea when I arrive and selling the furniture used when I'm ready to leave.
Why? I don't have that much stuff to begin with, and I try to buy used when I arrive in a new place. The only added cost is the plane ticket, and I probably fly less than the average vacationer.
Even if you're right, moving frequently is a fact of life for young people who grew up away from the west/east costs. It's the only way for young people who grew up in the midwest to launch a successful career.
Hometown --> college --> internships --> back to college --> grad school --> first job --> second job --> etc.
Considering the amount of glues and plastic required to make IKEA furniture I'm not convinced even at the 10 year mark IKEA is better ecologically, but that is a complex question that I wouldn't know how to analyse (if anyone tries I expect a few years latter someone will find a significant factor they didn't account for, and again a few years latter...)