That's often not the case, Amy. Plenty of acts of Morrissey's vintage are still doing well e.g. Paul Weller and Paul Heaton, with albums usually reaching no.1, not that that's a big deal in itself anymore (can be done on fewer than 10,000 sales).
The problem for Morrissey is not that he's 40 years into the job - it's that he suffered a catastrophic loss of fans and radio support between 2018 and 2019, for reasons that have been gone into countless times. 2017's Spent the Day in Bed was one of his biggest ever radio hits, and the early 2018 UK arena date was his most popular ever (most tickets were sold in late 2017 before all the Der Spiegel/For Britain etc. nonsense had really kicked in). It's this fairly recent seismic change in his fortunes that's the reason behind the current record deal situation.