You can search the internet and find lots of reasons why focusing on improving your FTP is a bad idea. I should say it’s not the worst thing but frequently it drives the wrong behavior and can take the fun out of cycling.
For many of us seeing progress is inspirational and keeps us motivated. That is one big benefit of FTP improvements. We think being motivated or at least consistent is the most important factor in performance cycling and health in general.
The bad part of putting so much focus on FTP is a few things. When you start to see FTP based progress, you think this is the best training there is. Hard/long sweet spot training can show some great results in short term FTP improvements for example. The problem is FTP is just a test, although in general your FTP or FTP watts per kilogram does relate to performance, specific goal based training and a wide variety of training produces better overall seasonal results. Also it’s very important to look at seasonal improvements not just short term FTP boosts. If you are continuously trying to boost your FTP, it will flatline. I think almost everyone realizes that periodization is important but then many don’t do a very good job of seasonal variety. Your FTP should drop down a bit and then build back up to new highs.
Also FTP tests have an anaerobic contribution so even short term sprint work will improve a ramp test for example but is likely not doing that much for your aerobic system. Aerobic changes come slowly over a long period of time.
Also when people are focused on FTP improvement, doing Zone 2 heart rate is very scary. They can feel they are not as strong and trying to do sustained threshold feels painful, oh my I am losing everything. But those that have the mental power to make it through a late fall / early winter of Zone 2 come out in peak form in the late spring with tons of motivation and realize this is the way forward.
Anyway, this is all very personal and depends on your circumstances and goals. FTP focused improvements can make sense.
Taking the cycling camp approach of a short 10 day boot camp period with doing cycling workouts everyday can cause some rapid boosts but this approach is not sustainable long term.