Frankly, I don't think that Gaga is the type of artist that can rest on her laurels and take her time. For some artists, having boundless creative freedom and a "fuck y'all, I'm doing for me" attitude can lead to great eras. Off the top of my head, Madonna, Prince, Kanye West and Rihanna are a few artists that can naturally put out great stuff when they follow their own instincts and work on their own time. For some artists, that kind of freedom can actually work against them, and lead to some really shitty product. Gaga strikes me as that kind of artist.
Which is fine, some people need that kind of pressure. I'll even admit that my own fave, The Legend Christina Maria Aguilera, does her best work when she's in a position of having something to prove. Stripped was born of an intense desire to prove that she wasn't just another pretty/blonde/brainless pop singer. Back To Basics came from the need to prove that she could be a creative artist.
Gaga made her best music, and had her most technically flawless eras (we're not just talking songs, but the presentation) at the start of her career...which a lot of people forget actually began on the back of being dropped from Def Jam. Gaga learned a very hard lesson at the very start of her career, which definitely gave her noticeable drive and focused her creative energy. If there was an ever an artist that needed to prove their mettle, it was Lady Gaga.
Around Born This Way, she foolishly allowed herself to believe that she had made it to a "point of no return" level of superstardom, and...well, we see what happened. You can argue that the music was still good (BTW is putrid garbage, but ARTPOP is serviceable), but there's no denying that the wheels had started falling off the wagon as far as everything else about those eras is concerned.