Sorry I don't have any experience with easy to use phones; except to say I would hate to do anything fiddly like Amazon orders on a phone. I use a 10" tablet for that sort of thing which is generally very good.   idk if you can get tablets which will work as a phone these days.

ageco* has a page(july 2024) listing some suggestions
idk if the same models would be available in the USA

The best mobile phones for the elderly
Examples of phones with big screens
Samsung Galaxy S23 Ultra – 6.8-inch display (4G/5G and most durable Galaxy smartphone range to date)
iPhone 15 Pro Max– 6.7-inch display (4/5G)
Google Pixel 8 Pro - 6.7-inch display (4/5G)

Examples of flip phones[larger buttons]
Doro6820 (4G)
Nokia 2720 Flip (4G)
TTfone TT970 (4G with WhatsApp)

more :
www.ageco.co.uk/useful-articles/money/the-best-mobile-phones-for-the-elderly/

*ageco is a trading subsidiary of the charity Age UK