You are right. About the disagreeing part
Jokes aside, I do get what you are saying (an arc about mc's struggles with his craft, without romcom shenanigans - something I would have loved to see... in
another manga
), but I also feel like what this manga
excelled in was the romcom with a reasonable fmc who were advancing their relationship rapidly and didn't take "boohoo i'm an otaku trash who hurts you by my mere presence" for an answer. A far-too-rare strength that is sad to see put aside.
Then it never delivered, over several arcs. And this arc is effectively acting to pause any romcom progress entirely, and reset things so author can milk it further in the future (for some reason jp authors seems to think that romcoms die when couples get together).
In addition to that, I find this arc
far too detail-oriented, going more edutaintional than entertainment (feels like author went all-in on research, and enjoyed it too much and needed some arcs solely to get to talk about the fun stuff he learned). And yet insists on further milking any and all "issues" wakana has, by not having him ever asking anyone (relevant) for help.
Some textile he knows he has seen but can't find in cosplay stores? He should obviously ask his dad, or specialized stores he has prolly been in before (could even have them unable to answer his query, just unrealistic that he didn't even think to ask them and only asked others instead).
Unable to get a certain strong white he desires? Again, ask specialized stores (instead of cosplay ones), textile or even down to the companies actually dyeing. And even then, his dad prolly knows who to contact when you need specific colors/patterns for your textiles.
Overall, too much details while at the same time too little (not enough to describe the entire thing), as well as describing long periods of looking for something without him ever realizing to go for low-hanging fruits as he's stuck - which makes it feel like something is inflated for 'drama'/tension, rather than being a realistic issue.