I have worked for the industry since 1997.
Not entirely for 19 years, because I had other jobs along the way, but I was very fortunate to work for a number of good game companies such as Electronic Arts, Ubisoft, etc..
I worked mostly as Quality Assurance and there were quite a number of people I've met along the way who didn't have a degree nor diploma.
I only have a college diploma myself, by the way.
We were always using in-house game engines, so it doesn't really matter.. in terms of deciding what game engines you need to learn.
What matters the most is how you're going to show the Human Resources people what you're capable of.
The Human Resources department of the game companies, believe it or not, are filled with people who don't know anything about games.
If you want to work for a game company, then they're the ones you need to impress.
I've used many game engines, but Construct 2 is the best game engine I've used.
Use Construct 2 to create at least 5 complete mobile games yourself, before submitting a resume to game companies.
If you're looking to work as a programmer, then you need to be fluent with at least one programming language.
My recommendation is C++.
If you're looking to work on other roles, then you don't need to be fluent on any programming languages.
They'll value a person who has extra skills other people don't usually have.
Remember, what they're interested are only the end products.
The ones that show you're the one who can make them a lot of money even after taking multiple people's roles at once.
I don't work for the industry anymore, because it's fun to play high end console games, but not to live with them.