IMO the problem is more than lower the input. I'd say only 0.3 litersperSqm isn't enough for fibers EDITED, see at the end.
After that, the ratio 24 fibers for 1 fabric isn't easy to understand, 4 to 1 would be more "credible". Lets say you have 8000 l/Ha of fibers, 2560€ in direct sale, with a 4->1 recipe you have 2000 liters of fabric, 8000€ value. It seems too much but actually your Onion crop give 8500€/Ha without the need of a factory (sugarcane give more so nothing weird ;) )
And finally your recipe gives 12000 l/month, more fabric than the vanilla cotton (7500) where cotton has a 4* liter price comparing to your fiber (0.32 -> 1.252) so for a global game balance fibers should produce less pallets than cotton (only 1.5 for wool), between 4000 and 5000 l/month should be ok, 16k to 20k €/month isn't a scandal and if you want to produce it all the year long you need between 24 and 30 Ha (51 for cotton) so you probably wont do that all the time.
All that for only 1 recipe :D (and for basics game prices per liter of course). I give you the 1st list I made yesterday with your culture fruits (as many of your productions need theses ressources I need to be sure these are final volume/prices to have the right number for balancing prods. I.e. linseed oil price and recipe will depend of the liter/Ha and price/liter). So if in your vision of the gameplay you want to change some values, tell me.
https://www.transfernow.net/dl/20250730mfuwX1TC
EDIT: I made a quick try and I understand that you split Lin into 2 plants, 1 for seeds only and an another crop for fibers only where this one (as hemp) don't use the: <harvest litersPerSqm="0.3" but only the windrow part. In vanilla game even grass use the "harvest" value that's why I was a bit lost . So it's not 3000 liters/Ha but 50.000... (11000€/Ha for hemp and 16000 for flax). Your recipe is still unbalanced (50% of the fibers value) but now if there is a problem with the litersperSqm it closer to "too much" than not enough.