Hmm I'm in two minds about this. I think that yes if approached with sensitivity and taking the lead from the person you are speaking to its OK but that it's not ok to tell people that all they need to do is persevere and it'll work out in the end. It absolutely didn't for me.
I have mixed fed 3 children - despite desperately trying to ebf. I have had support from midwives, health visitors, breastfeeding support workers, groups, mumsnet etc. I have expressed round the clock, gone through the cluster feeding, skin to skin power pumped, compressions, various herbal teas, loads of water, fenugreek tablets, oak cookies etc. Nothing worked for me and the doctor wouldn't prescribe doperidone.
My supply has always been the issue.
DC1 she would just knod off when feeding - EVERY time. Nothing would wake her and eventually the midwives pressured me to top up with formula. The formula of course messed things up. With A LOT of work I did manage to increase my supply by the time she was 5 months old and we managed about a month of no formula. Then at 6 months she started biting and wouldn't stop and by that point I just couldn't do it anymore.
DC2 was similar and just kept sleeping and not eating. In the end she screamed and screamed so much and just couldn't get from me what she needed, that I gave her formula. I spent most of my time with her on me trying to breastfeed, top up, express and then I'd be up in the night expressing too. I found it incredibly hard when she'd want feeding at say 8am and then I'd feed her for 30 mins and then we'd need to go to school and shed scream there and back because she wanted formula. It just didn't work. I could give her the formula and she'd be full in 10 mins and happy vs devastated when being breastfed. Plus I wasn't ever able to give DC1 the attention she needed because a "feed" would take around an hour every 2 hours once you factored in bf+ff+expressing - it's not like it was say the first 6 weeks, this went on and on. In the end I was so exhausted and I was verging on depression from it all I just stopped at 3 months. I just felt society thought I should be breatsfeeding, which is why I persisted for so long. If you'd come up to me and said I should persist and it would be worth it in the end it would have tipped me right over the edge.
DC3 is now 9mo and I'm still mix feeding now but I have very little milk. It's so disappointing and should have been different. All went well for the first 4 days until she was admitted to hospital with a serious infection and put onto IV antibiotics. They weighed her and she'd lost 14% of her weight and also diagnosed with cmpa due to rash/vomiting/diorreah/excessive wind. So they moved her onto special formula. She was also diagnosed with tongue tie. Perhaps some people would have battled through but I couldn't risk my mental health. I exclusively expressed while there but I also had a post natal infection. When she was discharged from hospital a week later and I was better I cut out dairy and resumed breastfeeding alongside formula but much as before my supply never recovered. I have tried everything i could but have to accept that it is what it is and have given up on the hope that I'll ever ebf. Aside from anything I've had a 2yo and 7yo to look after as well and it has restricted me from having the same success that I did when I only had DC1. Still, she's 9mo and that's the longest I've managed and at the very least it gives her comfort and a bit of my milk. Again, if you had at any point told me to persist then the pressure of it probably would have had the opposite effect.
I don't really think it's as straightforward as saying to women to persist and it'll be worth it. It's simply not always true. I think you need to find the right outlet for it, so that it's well meant advice and reaches the right people.