Why is axi bus popular for fpga?
AXI bus is efficient for high throughput data transfers. If you have simple peripherals the procedure is to use an AXI to APB converter and drive all your simple peripherals from the APB bus.

AXI is great if you have e.g. an USB/PCIe/Ethernet core. You add a AXI master and it pushes the data straight to memory, using very efficient data bursts.

I have used AXI for many years and found that nobody in ASIC land implements the full AXI specs on their chip, even within a company. The most complex parts are dropped to reduce logic, which gives interesting stories if AXI IP comes together...

What caught my eye is that a lot of smaller cores (even those from the manufacturer who has set the AXI standard) do not use the full AXI capabilities. The core datasheets I have seen say "You will only see single transfers cycles coming out of the core."