"My Photo Stream", to give it it's full title, is now a legacy app - that is to say that if you had it on a previous iPhone and used it and had a BU of that device, that app was "passed on" to your new iPhone, up to and including iPhone 13; but possibly not to iPhone 14 onwards, as far as I can see.
Moreover, if, for example, you had an iPhone 13 or earlier with an active "My Photo Stream", then wiped it clean and gave that device to another person, then "My Photo Stream" would be absent.
I still use it on my own iPhone 13 Pro and it works fine. As I'm sure everyone who used this facility knows, the automatic transfer of photographs to your Mac does NOT include videos. These have to be transferred by USB cable to the Mac.
Transfer of pics from iPhone to Mac can be achieved in other ways of course:
1. By cable.
2. By turning on "iCloud Photos" on your iPhone (Settings > Photos > iCloud Photos) and doing the same on your Mac (Open Photos app > Preferences > iCloud Photos).
NB this can gobble up your free 5GB of storage very quickly; so you might need to consider splashing out 79 pence/cents per month for 50GB or 2.49 GB Pounds/USD Dollars per month for 200GB of iCloud Storage.
Although I think the basic free 5GB is really mean of Apple, the layout of 79 pence/cents or even 2.49 Pounds/Dollars per month is hardly going to break the bank - compare these costs to a cup go coffee!
Just a few thoughts of my own.
Ian