Over all I am pretty happy with my apple pie. I make one pie a week for someone I cook for. But I am not satisfied with the consistency of the firmness of my apples. Sometimes a little too crispy still and sometimes a little overdone and sometimes a mix of both. I have one cooking now, I started it off on 425 for 15 min, reduced to 325 for 30 min and not reduced to slighlty below 300. I am thinking if the juice is boiling out for maybe 5 min or so they should be done but just not sure about that.
Why dont you cook the apples into a pie filling before putting it in a crust. I precook my bottom crust to about 1/2 done, add filling and lattice the top. And cook til the crust is golden brown. I find the bottom crust doesn’t get soggy this way.
But your pie should be done when your top is brown by your method.
My top gets brown more than 30 minutes before the apples are done. Years ago I used to precook my apples like you mentioned. I may just go back to that. I just pulled this one out of the oven. Cooked almost 90 minutes on a little lower temp. I will know in a couple of hours.
If it’s in a box at the supermarket, it’s probably done.
That’s how I make them, anyways. 
It also REALLY depends what variety of apples you’re using. Some hold up better to cooking, staying firm and keeping their shape. Some break down quicker. Some turn to mush instantly (McIntosh, I’m looking at you). More here
If your apples aren’t soft enough and your crust is already brown, cover it with foil and continue baking.
Well, this one came out in the acceptable range, just slightly softer than I like but ok.
I’ve found that Granny Smith apples are the best for baking.
If you don’t want to pre-cook the apples, you can macerate them to soften them. Just toss them in the sugar and spices they’ll be cooking in and let them sit for a while. At least 30 minutes, and up to about 3 hours. It softens them without actually cooking them.
Once they’re macerated, you can add any flour/starch you might add to thicken the filling.
Also, I second the cover-with-foil method if your top crust is too done. OR you can use a buttery crumb crust, too. I stink at making a pretty lattice, so I often do a Dutch apple style.
I have been using the store bought pre made crust lately. Granny smith apples. I am suspicious my oven is hotter than I think it is. This one came out good cooking 50 degrees below recommended.
I’ve always used “when the filling is bubbling through the slits” the pie is done. You may want to cover the edges of the crust with foil to prevent excessive browning; remove the foil the last 15 minutes. My Betty Crocker recipe I use has the oven at 375F for 45-50 minutes, which seems to always work.
As others have said, try different types of apples. Around here Haralson are the preferred choice, especially when you know someone who can give you several bags for free in the fall.
I always thought it was a matter of how thick you cut the pieces; cut them thinner and the heat doesn’t have to penetrate as deeply, so they’ll be done sooner. I use a mix of Cortland and Granny Smith, cut half-an-inch thick, and it always turns out great.
To find out if an Apple pie is done, ask Siri.
For Amazon pies, ask Alexa.
The bubbling makes sense. I know apples cook very quickly once they reach temperature. last week I pulled the pie out when it first started bubbling. This week I gave it about 7 more minutes and it seemed to work. I will also try the tin foil.
I cut my apples into 1/8 wedges, my mother always 1/4 hers and they seem to cook perfect.
I test for doneness by sliding a bamboo skewer into the fruit, through the slits on top. You can easily tell if the fruit is tender or firm this way.
I also like Granny Smiths because of their flavor-forward tartness. I slice them 1/8" thick on a Benriner slicer so that they’re uniform.