I think you've put the main reason for your lack of motivation third on the list - depression, you can find away around the other reasons if the motivation was there.

I've always struggled when it comes to the scenery - I would begin my layout enthusiastically and then reach the scenic stage where my confidence would wain and before I knew it a new idea for a new layout took hold and off I went in a new direction.  It was only last year that I finally accepted that I couldn't keep buying stuff for each new project and then see myself with too much stock and no railway to run it, then I sold off a good proportion of my stock.

During some counselling last summer I had an epiphany - my incessant need to purchase was dopamine driven, it was the thrill of the finding and making the purchase - once I got the item it lacked any thrill and then made me feel bad that I had bought something I didn't really need - it's a sign of an addiction.

I've also accepted that when I become obsessed with a new layout plan it is probably a sign that I am depressed and this is how I look inward into myself, falling back onto a comfortable pattern of behaviours.

What's changed in the past few months is that knowing why I purchase stuff and why I make plans that I wont actually deliver is part of repeating patterns of behaviour that do more harm than good.  I've not purchased any railway stock since last summer, what I am buying in limited amounts are scenic items - paints, gravel etc and I am working towards finishing a railway and only once it is finished can I think about my next railway which will utilise some of my N stock.

Take the rest you owe yourself, sort out your head and then come back to modelling but pick something small and achievable, look at the Billy Bookcase threads - simple baseboard, simple track.

I typically use NHY581's Mutton as what can be achieved with simple track and baseboards, but I've also been looking a Ladmanlow sidings (Mutton inspired actually) as well

Can I also recommend you find yourself a local mindfulness or Buddhist group - those groups can transform people's lives.

Definitely empathise with this and I'm sorry you're having to deal with it mate. I've had to take a 12 year break from the hobby, with only minor indulgences inbetween, because of similar struggles. But you know what's great about that? In the intervening years, the hobby has advanced tremendously. The fact that I now have a Sentinel, Cargowaggon, Polybulk, and PBA "tiger" hoppers, sat in boxes in my drawer, is more than I could've dreamed and it's opened a lot of doors. Added to that is the Hornby 08, Dapol class 22, various other clay wagons by DJ Models and Dapol, Hattons coming out with the definitive class 66, and Bachmann retooling their class 25. Winding the clock back 12 years, that stuff would've been a HELL of a lot of scratchbuilding, kitbuilding, and superdetailing! I like scratchbuilding, but not 98% of my fleet!

If you can find the motivation to check him out, I can highly recommend the work of Dr Jordan B Peterson. Whether it be his book, 12 rules for life, his interviews on podcasts such as the Joe Rogan Experience, his youtube videos, or the online Self Authoring Suite... this guy has probably helped more people, particularly men, to get out of depression and get their life back on track, then any other psychologist at any time in history. Truly an extraordinary guy and his work has helped me immensely.