It depends what we need/expect from each player. If we buy an aging player and need them to perform like they were 25 that's on us. If we buy an aging player and accept that they are a contributor, not the centre of our attacking plans, that's more realistic.
Our problem last season was that we had several players below what we wanted from them for some time at the start of the season: Roly, Gui, Kosta, Watson and Mikey was injured for a long period of time.
If Gui had contributed as he did, but the other players hadn't also had poor season, we'd have been less unhappy with him.