The decision of dropping should be taken by an individual , what I can help you is with analysis part.
You might end up in one of the two categories:
(1) You know what went wrong last year and have a list of topics readily available that you need to focus on, improve by reading standard books, solving gate problems and get better at it.
(2) You feel like you gave everything this year and you were just unlucky this year.
So if you belong to the 2nd category and feel that your preparation and was very good and was probably unlucky.
Step 0: (compulsory for category 2, optional for category 1) Give last 10 years and get your average marks and prepare a record something like this:
15 days at max.
Know your average. And formulate the list of your weak topics, your average can't be above 80 in the above mocks and get below 60 in actual Gate Exam.
Next: You belong to same situation as category 1, with list of topics/subjects you know you need to improve.
You have the list of topics ready with you and if you think you can work hard and complete them then go ahead, if you have a mindset of leaving some portions again considering them hard and hoping that they won't show up in the exam next year, I don't think you should drop.
So after completing all the weak portions and revising the strong one evaluate yourself first. Are you prepared for Gate ?
Give the mock exam again and try an average of above 80(Target single digit rank, every year topper's marks is more than 80 however hard/easy the paper be). If you do these you will be better prepared.
After that if you wish you can start with test series and other practice portions to fix things like time management ,anxiety ,Hall management etc. but first get your concepts fixed. If you score in 50s or 60s in previous years, don't expect a miracle on Gate exam day.
Now if you think about age issue I have two examples for you:
Namita Kalra : AIR-1 (2018)
2014 passout https://www.cse.iitb.ac.in/~namita/education.html
Kishlay Das : AIR-37 (2017)
If you know few more of such example you can comment the same in comment, so others will also know it and be inspired.
And I also gave gate for 3rd time and got AIR-175 in 2019 (2017 passout) so I guess, you can also.