I can understand you being frustrated by this. However I may well have said similar things in the past.
The truth is I work 3 days a week, I have 2 gorgeous sons aged 3 and 18 months who I conceived the first month of trying, a very supportive and lovely dh and supportive family (albeit at the other end of the country). I love my life. I have a fantastic life and often marvel at how lucky I am.
Yet often just getting through the day overwhelms me. At times liek this I am gobsmacked that people do all this with no dh, no family, more than 2 children, smaller age gaps, and disabilities / illness (both of them and dcs) to contend with. How on earth do you cope i think. Not because I wouldn't cope - of course i would if i had to, you can hardly send the dh or dcs back if it doensn't work out as you plan can you? I don't mean it to be patronising or belittling. I am just trying to empathise and show appreciation for the tough time you have.
I can see why you take it as you do and that when you hear it for the 50th time you feel liek saying 'change the fucking record love'. But I am sure it is not meant like that.
Not the same at all but I get similar comments about my job as a surgeon. 'Oh you must be so selfless' I get. Um no, I am incredibly lucky to be allowed to do a job I love, selflessness has nothing to do with it at all!$ So although not anything as emotive but I kind of get you. Just think that people are probably more well meaning than you are giving them credit for