Worked for me, but you will be flamed for even mentioning them on here, or in RL. I have 4 DC - all quite different and it worked for them all but I got a hell of a lot of grief for it - with the first two anyway, with the twins I was told by everyone (HCPs and friends included) I would absolutely NEED to have a routine - the things I had done with the first two and been totally lambasted for, were suddenly not just ok, but recommended for the last two.
DC1 - totally chilled out baby and fully BF until 5.5mths when we stared weaning. On the smaller side at birth but not ridiculously so (25th centile)
DC2 - complete opposite of DC1 - average size at birth (50th centile) but was overdue and very quickly dropped to natural centile which was around the 2nd (at some points off the bottom of the chart). Severe reflux meaning feeds were very difficult and severe eczema meaning bath times and nappy/clothing changes took forever because of all the creams etc - an incredibly fussy baby. BF until 3m when switched to hypoallergenic formula.
DTs - premature so both very small (less than 5lb when they came home) and much sleepier than previous two had been due to being prem. Reflux again, but no eczema and generally less fussy than DC2 as pain was managed very early, but still massive vomits daily. Both on hypoallergenic formula before home from hospital.
In all cases I had no wider family support at all as all lived hindered of miles away, and in the case of the DTs a routine was essential because I had to get DC1 out to school and activities etc.
All four slept through 7pm-7am by 4 months.
DC1 did 7pm-12am-7am at 10 weeks, DC2 did the same at 8 weeks and DTs did it at 6 weeks.
You do have to read the books with your own mind - I did not eat a banana at 8am because Gina told me to, but her principles of eat lots through the day and sleep less so that at night they are full and tired make a lot of sense. The routines are also very helpful to babies and to parents - I found them incredibly freeing because I knew when a feed would be needed so I could plan around that. The first 2-3 months are the hardest for sure, but the hard work pays off.
You do need a wise head on your shoulders however to be able to read what the essentials are and dismiss the extras that aren't really essential (like that banana at 8am), and to be able to make adjustments - like my DC1 fed in 15min flat - even during growth spurts it was only ever 20min so I had tons more time than the book suggested to keep them awake and entertained because feeds were way shorter.
You also need a very thick skin because you will be called terrible things and criticised to high heaven for doing it