ADVE
Matthews Asia Dividend Active ETF
stock NYSE ETF

I don't know - everyone is different. There are people out there who can be 100% equities and stick with their plan even during a 50% decline like during the Great Recession (I know because I did it at the time - though admittedly, I was only in my late 20s then and didn't have nearly as much invested as I do know, so the numbers didn't seem as scary then and I also knew that I had a **long, long** time to go and that if things didn't rebound we'd all have a lot more to worry about than the value of our portfolios), but most can't no matter what they think or say.
Personally, in my non-401k accounts where I'm not limited to what is offered in the lineup, I use a combo of SPYM and AVUV to somewhat replicate the broader US market, I used a combo of ADVE and AVEM to replicate the broader international market, and I use VPLS (plus some individual bonds) to get some bond exposure. I target about 10% bonds and I split my US/international equity about 70/30.
That said, I was essentially 100% equities until about 2-3 years ago. So, I added 10% bonds around age 45. I will likely add 5% every 5 years until retirement (though I may wait until age 55 to go to 15% at 55, then 20% at 60, etc. - I haven't decided for sure on that part just yet).
But, my approach is not necessarily the best for everyone.
If I was telling my kids what to do (at 9 and 13, they're not out on their own and old enough to invest on their own yet) and they didn't want any bonds, I would tell them to use VTI/ITOT/SPTM for their US and AVDE/AVEM for their international, pick a split they like (I'd suggest 70/30, but anything between 20% and 40% international is fine IMO) and let it ride.
If they wanted bonds, I'd tell them to throw 10% into VPLS.
At the end of the day, people can, and will, do what they want and you can do worse than 100% VOO. I just don't personally think being only in the S&P 500 is the best approach for anyone, even if you want to go 100% equities.

I don't know - everyone is different. There are people out there who can be 100% equities and stick with their plan even during a 50% decline like during the Great Recession (I know because I did it at the time - though admittedly, I was only in my late 20s then and didn't have nearly as much invested as I do know, so the numbers didn't seem as scary then and I also knew that I had a **long, long** time to go and that if things didn't rebound we'd all have a lot more to worry about than the value of our portfolios), but most can't no matter what they think or say.
Personally, in my non-401k accounts where I'm not limited to what is offered in the lineup, I use a combo of SPYM and AVUV to somewhat replicate the broader US market, I used a combo of ADVE and AVEM to replicate the broader international market, and I use VPLS (plus some individual bonds) to get some bond exposure. I target about 10% bonds and I split my US/international equity about 70/30.
That said, I was essentially 100% equities until about 2-3 years ago. So, I added 10% bonds around age 45. I will likely add 5% every 5 years until retirement (though I may wait until age 55 to go to 15% at 55, then 20% at 60, etc. - I haven't decided for sure on that part just yet).
But, my approach is not necessarily the best for everyone.
If I was telling my kids what to do (at 9 and 13, they're not out on their own and old enough to invest on their own yet) and they didn't want any bonds, I would tell them to use VTI/ITOT/SPTM for their US and AVDE/AVEM for their international, pick a split they like (I'd suggest 70/30, but anything between 20% and 40% international is fine IMO) and let it ride.
If they wanted bonds, I'd tell them to throw 10% into VPLS.
At the end of the day, people can, and will, do what they want and you can do worse than 100% VOO. I just don't personally think being only in the S&P 500 is the best approach for anyone, even if you want to go 100% equities.