Ummm.
ME1 is old, that is why a lot of the issues you bring up exist. E.G:
-Texture Pop in: Welcome to the days when graphics were bad. That was actually ok for the time. Not great, but not terrible either.
-Inventory: Its a proper RPG inventory, back from when Bioware made more old-style RPGs. Its not a matter of it being rushed.
-Horrendous balance and combat mechanics: They were trying something new here. Merge an RPG with a shooter. IMO still got the balance better than ME2 or 3. The RPG was a lot more prominent and one, and the shooting was a means to the combat end, rather than the focus of the game. As for the shooting being a sign of it being rushed, play ME2. That was chest high wall corridor shooting. THAT is rushed, meanwhilst ME1 had preplaced enemies at each location, that rewarded you for how many you killed and how you dealt with them, and were there based of testing of the balance. I think the solider was probably used for this testing, as its the only class [Maybe Adept is included, but I generally don't play adept] that has a really easy time of getting through the game due to its regenerating health and full weapon specialisations, and heavy armour.
-Backwards difficulty curve: Please explain. If you mean it gets easier as you go along, welcome to RPGs. You get stronger as things go along, and thus things become easier. It depends on your build, but it is a mechanic there so that if you're say an engineer in ME1, and go for full electronics and decryption and intimidate and charm, just so that you can unlock everything and use all dialogue actions, you're not completely screwed when it comes to combat. You'll notice the same thing in Skyrim, DA:O and most every other RPG I've played. Build your character right, and things just get easier.
Also, get the PC version:
-Texture pop in/out is nowhere near as bad.
-Fast loading of areas.
-There are actually Journal, Squad and Inventory buttons on the keyboard. In ME2 and ME3, I have to open the menu and make my way to each to open it. ME1, just press one key on my keyboard. Win.
Also, things that are more rushed in ME2 and 3:
-XP generally given at the end of the mission rather than during it. In ME1, the amount of XP for all mutually exclusive paths was perfectly balanced so that if you took one option, you'd get the same amount of XP as if you took the other. Completionists would get more XP, but that's because they worked for it. In ME2 and I believe 3, the lazy route is taken. At the completion of the level in 2, and I believe an objective, or maybe the mission in 3, a flat amount of XP is given. There is no careful planning so that if you work for more XP you can get it, or so that every option is balanced to give you an appropriate amount of equal XP as all others - its just a flat XP amount given at the end of the mission to take out any calculations and make the process easier.
-More areas, more sidequests, more exploration, larger areas, more to do - ect. in ME1. Whilst it was cut and paste for SOME areas, there was more of it. Cut and paste was likely to reduce disk space, not for rushing. ME2 and ME3 combined don't add up to the time I spend in my ME1 playthrough - and that's including all the ME2 planet scanning that wastes so much time. Seriously, you want cut and paste, that planet scanning is it.
If you say I'm wearing Nostalgia glasses, no. I'm playing ME1 right now. It is as I am describing it. Next, I'm playing ME2, then ME3. I have played all side by side before, and recently. I know what I'm talking about, and I'm not using Nostalgia glasses.