My point is that Sony hasn't relied much on third parties for the success of the PS4 as they have made their first party games the main attraction with being huge, blockbuster productions. Of course third party games sell consoles too, but they have spent this entire gen strengthening their studios and increasing the scope of the projects they make. They learned during the PS3 days that the games they make are their best shot at winning the market and they have only doubled down on that during the PS4 era.
It is still not true at all, Sony was always trying to have a strong first party but their efforts needed time to materialize and translate to the mainstream, but they have been actively trying to be a strong first party from the start. still they are more aggressive with third parties than they've ever been, but maybe you are not really watching:
The marketing deal with Destiny 2 was huge for Playstation and key for their success, and Call of Duty Black Ops bundle did play its rule too. those 2 were key and gave them an edge over the competition.
They funded Street Fighter V which gave them the edge in fighting genre, last gen a lot more people used to to play SF4 and other games on Xbox 360.
They funded Bloodborne and signed exclusivity deal for Ni-Oh and win over Souls lovers.
They made a 1-year exclusivity deal with Activision about Crash Bandicoot Trilogy.
Final Fantasy VII is a timed-exclusive.
Resident Evil VII VR is exclusive for PSVR to this day.
Looking how DQ11 was late 2 years in Japan i think it was probably timed console-exclusive.
Man, they are even doing those kind of deals even with small titles that don't sell too well like KoF XIV which was PS exclusive for a year. I'd argue that Xbox not doing the same is really hurting them and making them lose mind and market share.