I've noticed a few people on here and other threads, who are really struggling, feeling deflated/broken and sad in their current position at work.
When you are in that place, you can't relax, you can't switch off and you defo don't really live. All you live and breath is dreading the following day back in there once again.
So it can be really hard to find the energy or time to even consider applying elsewhere. You start to wonder will it be different there? Is this how it's always going to be? and you can actually talk yourself out of it. Mix that with work colleagues telling you most days (and helping you to feel most days) that you aren't worth much and you are useless and you have the perfect storm to take away not only your self confidence, but your self belief.
When others then say the simple enough sentence "apply for a new job", it's not so much stating the obvious, it's actually like an inner voice talking to you from outside. You know in your heart that you must move on, but having been so battered mentally by those around you, on a daily basis, you can lose the ability, will power and just belief that you are a commodity worth having elsewhere.
What is one person's trash, is another person's treasure and I can tell you as an older person, who suffered and endured crappy jobs and teams around me, that every day you sit and tolerate that barrage of abuse, it chips away at you, your heart and your soul.
Once you make steps to rescue and remove yourself from that horrible situation, you will feel a little calmer, happier and easier on yourself. Right now, many companies are desperate for new staff.
Find some Recruitment Agencies who cover your field of work (like legal, project managers, etc) and get your CV up to date, focus on your positives, things you know you do really well and make them your keywords that stand out.
Send it to all the Agencies (not just one) and let them know, you already have a job, but would like to "further your career" "expand your horizons and knowledge base" "have room to grow and achieve" - slap a few quid extra on your current salary (oh gowan then, another £10K per annum) and see what comes offered back to you.
Every interview gives you confidence, let's you practice, so don't view any as a waste of time. Oddly, you may even find a cracking unexpected job offer lands right in your lap.
I know from what you've posted
@TheGlossy that you work long hours (so you are dedicated) you are concerned about the product (so you care) and that you give your all, even though you aren't receiving as much back. That makes you a desirable commodity in the work industry.
Find your niche, find your place, it's not where you are, this is temporary and soon you'll be somewhere you need to be and will feel more settled.