HL2 was quite a graphic intensive game at it’s time, certainly a fair leap from its predecessor.
If you can get anywhere near turning any settings down then you might struggle through with it, but ultimately you’d need a dedicated chip to enjoy it how it’s meant to be.
Add that to the fact the Mac source code is new and is using Orangebox source not the old HL2 source. Try running Portal on your 7 year old PC it won’t like it.
I got a new GFX yesterday as my other one was overheating, DX11 is good ain’t it.