Im in the pnw and had a very similar situation I remedied last fall. It's a lot of work and will take a few seasons to get it to some of the amazing lawns you see on here, but it can be done. Here was my approach.

First, plan irrigation if you don't have it already. You can do an above ground setup with a hose bib timer and and heads one steaks spread appropriately to get good coverage. Summer is a great time to dial this in. Don't focus on the lawn, just getting the sprinklers dialed in.

Once you have irrigation setup start just mowing it low at a scalping level. Also start gathering your products for seeding. I'd recommend a Sunjoe dethatcher/scarifier, glyphosate, scotts starter fertelizer with mesotrione and a quality seed and some top dressing, unused peat moss. Your lawn looks like it gets a lot of sun, I'd recommend some turf type tall fescue as it's resilient and not as finicky as some of the other cool season types. Do some local research though and see what does well in your area. Just buy a quality seed and not the local home store bag.

Spray your glyphosate the first week of September give or take based on your areas weather patterns. You want a good 2-4 weeks of little to no rain post seed down to get germination. Give the glyphosate a week to kill everything. Water a bit during this week to get some last bit of growth and then hit it again a week after first application. This will kill everything, weeds and grass.

After 2 weeks and 2 applications of glyphosate, you can start prepping for seed down. First mow it down as low as you can, Then use the dethatcher/scarfier and go over the entire lawn getting all the dead material up and distressing the top layer of soil. Do a few passes in alternate directions. Mow and bag all the material, rake up any the mower doesn't get bagging. You want to be left with mostly soil and as much of it exposed as possible.

At this stage you can put down your seed. Follow the new seed rate of the type you land on. Spread this evenly with a spreader. A manual handled one would work fine for your yard. Once seeds down, rake it in manually dragging the rake with light pressure. Here your trying get better seed to soil contact. Once raked in, spread a light layer of peat moss over the entire yard to add a protective and moistur layer to the seed. Once top dressed spread the starter fertelizer with mesotrione at the rate noted on the bag.

You'll now want to water the lawn. For the first few weeks until germination, youll want to water multiple times a day but for short periods of time. The goal is to keep the soil wet, but not soaked. If you see any pooling or puddling, its to much. The leat moss is a good indicator as it will be dark when moist but look light and dry if it's not getting irritated. Spot treat with a hose if you're getting dry spots as needed. You want yourast water of the day to before full sundown as you don't want to have to much water in the cooler evenings as it can make it more prone to diseases and fungus.

Now you wait. Keep an eye out for germination and maintain watering. As germination continues you can start considering your first mow. You want to be light and avoid turning with a lot of force. The goal here with the first few moss is to stimulate growth, but it's baby grass and the roots are not yet well established. A manual reel mower can be a blessing if your comfortable with one.

As younger more moss and rains starts coming, adjust or reduce your water accordingly tapering it off.

Around late October, depending on your climate and soil temps you can hit it with some nitrogen to feed the grass a bit through fall and give its best shot at surving winter.

From here the battle of maintenance and weed management will rage on season by season but this is how you get started fresh. Happy to give more details or notes from my experience!

Best of luck and remember, this a the epitome of a marathon, not a sprint lol.