I believe that these spammers now concentrate their efforts towards e-mail addresses hosted by major providers, like Gmail.

The reason is that I have an opposite experience, during the last couple of years I have received much less spam messages than before.

I have hosted my own e-mail server for more than 2 decades. Previously, I had to filter large quantities of spam messages, but lately the number of spam messages is much less than 10% of the total number of received messages.