It is the responsibility of the taxpayer to support the claims that they want to put of the tax return. https://itsdeductibleonline.intuit.com/ is still available and is definitely a good starting point. The preparer seldoms gets to see the goods donated, so it is very hard for him (or her) to determine their value. Our experiences and knowledge lead us to possibly question some items presented to us, but we are not the auditors. 

Personally I point the client to https://itsdeductibleonline.intuit.com/ or a short version sheet that is printable, such as in Tax Tools https://www.taxtools.com/products_tt.aspx Which is my go to support product for many things.