Since my monitor has HDMI, the Mac mini HDMI input is very convenient!
Replying again to word this another way:
With a HDMI port, it's marginally more convenient for you to plug your display in, but it's literally impossible for someone else to plug 3 non-HDMI displays in.
With the feed that runs the HDMI port available over a TB3/USB-C port, it's (possibly) slightly less convenient for you (you'll need a different cable, or an adapter), but it's usable by someone else who wants to use 3 non-HDMI displays.
This is the aspect that most people who argue for legacy ports mostly never admit or acknowledge, and often just outright deny. That special-use port, is not used by everyone, and it's entirely possible (if not literally already happening) that accomodating that special use port, detracts from more flexible capability.
"Ok you can have two USB-A and a fast card reader.... oh but by the way you lose a TB3/USB-C port".
You (as a group, not specifically
@Stella) want something specific because it's marginally more convenient. Some of us want something that's as flexible as possible, to any number of scenarios/future uses. I've got a 2011 MBP sitting around here. Do you know how many useful ports it has in 2021? Two. Gigabit Ethernet, and Thunderbolt 1. The USB ports are too slow for anything useful, Firewire devices are basically not produced any more, most ExpressCards use the bigger form factor.
It's usable (or was until the GPU **** itself) purely because the TB1 port offered PCIe lanes externally, which could run a dock, with other/newer/more high speed ports.