Total accounts has a low impact on your credit score, and one account won't make a difference. I have a 750+ score and 10 accounts but that is still "poor." I think you need something absurd like 20 or more to get an excellent rating in that section.

Age is average across all accounts and counts for a little bit more but is still way less impactful than derogatory marks, payment history, and credit utilization. A better way to improve your score is to lower your credit utilization by asking your already open credit channels for credit increases (call or go in-person which will probably be a soft pull rather than a hard pull which can affect your credit if you have too many)