I mean, it can be solo'd rather easily, since it does no damage. It has no special moves, like Baron. I remember when you implemented the new SR, you made sure Baron felt like a boss.
It does almost no damage, which makes it hard for teams to engage on whoever is doing it, unlike Baron, which chunks and shreds everything in sight.
But even then, Elder is too tanky to be fun to fight. With a full team, it takes forever to do it. I've been in a game where the two teams decided to trade Baron for Elder, but the Elder team took so long that the Baron team actually had time to finish Baron and run all the way down to pick a couple people off as they were finishing it. That's how long it takes.
For a buff that impactful, it doesn't feel "Boss" enough.