There are a number of abandoned games that it would be great if someone picked them up again, carried them on to completion.
There are some problems with this:
Many times when a developer abandons a game they are hard to contact. Patreon could be shut down. There could be no email address to contact them. They are probably not hanging around these parts.
Okay, so now imagine you get lucky and you actually contact the guy. They are on board with you taking over their abandoned project. They may ask you to pay them some money to have the rights to the project they abandoned. Say everything goes well and you get their blessing...
You are probably going to need to get all of the assets that they were using, but much more likely you will just need to start the project over.
The game could have had problems. For example plotholes, or bad pacing at certain points, or poor renders that need to be redone at other points. You will also want to keep things consistent. There could be a much hated character like Eric in Big Brother that fans may not want to be in a new version.
Then you gotta contend with your mission project.
Do you want to complete the game as the developer originally intended?
or
Do you want to complete the game in your own vision?
These 2 things could be very far apart.
A lot of times people just make a remake of something without going to the original developer.
"Big Brother Remakes" could be it's own category in search. That's how many of them there are. Dozens of them exist for just that 1 game.
You are not going to get all of the support they may have had.
Most of the time it makes far more sense to just start a new project, and you could obviously use an older abandoned game as a source of inspiration in doing so there is nothing wrong with that.
I have never once seen a game get a completed tag after a developer abandons it and someone else picks it up. Keep that in mind.
There are some pretty great abandoned projects collecting dust. Games like "My Sweet Neighbors" and "Our Fate" come to mind. Both of those games for example could possibly be a success if revived.
I will use "My Sweet Neighbors" for my example.
You don't need to make it as "My Sweet Neighbors Remake" for the title...
You can call it something totally different like "Love next door" or whatever you feel like.
You can make similar characters to the game, and customize them and give them your own little twist.
You don't need to make a perfect replica. That game for example has been abandoned for over 5 years now. The initial release was like 7 years ago. So, I'm sure there are better assets available now. So, you can have the new neighbors be even prettier. Do you really want to use the same apartment they used? It has been in like 917 adult games by now.
The coding of the game was interesting. It had a little heart icons and and I think it had like a "Trust" and a "Love" meter for both of the main girls. You could pop a copy of that abandoned project onto your machine right now, and look at it's code and then copy the chunks of it that gave it it's feel, and remake that portion in your new project.
You can play the game over a dozen times and get inspiration from it's characters to make your own.
Then at the end of the day...
A brand new project, with new assets and starting from scratch would be superior to an attempted continuation from version 0.12 onto 0.13.
I think that game included some unnecessary characters and secondary love interests. You can chop those right out.
The protagonist was an office worker. You don't "Need" to give him that job. Give him any job you want.
The game made it so you were locked in with a love interest for the mom, and had no choice to go after the daughter instead...
You could remake it so you can choose which to pursue!
Fuck enough rambling from me!
TLDR: Just make your own project, and use a beloved abandoned project for a source of inspiration, and possibly snag some of it's code if you want to salvage a piece of it that is up for grabs.