There is usually a good reason for a dog being on lead. Please give all dogs on leash the space that they need.
You may know that one of my dogs spent some months doing rehab due to an injury. She still acts like a puppy and is a master at hiding any hint of being in pain or injured. She also loves to play with other dogs. To manage her injury, we needed to restrict her from playing, but also exercise her in a safe and controlled way. To ensure that she still had a great quality of life, her walks progressed from being in the house, to in the back yard, to out in public.
One of our greatest challenges was finding places where my dog could be exercised safely and without friendly dogs asking her to play.
Other dogs that I have worked with have initially been so eager to play with other dogs that they would pull their owners over. The owners spent their hard-earned money and time to teach their dog how to walk on a loose lead. They started by working in tightly controlled environments and then gradually work up to being able to walk on lead, at a great distance from other dogs. An off-leash dog, approaching these on lead dogs can undo all this work in a matter of seconds and put the training back by months.
So the next time that you see a dog on lead, please remember that they may have a good reason for being on lead. You can help them by ensuring that your dog is either put back on lead until they pass, or that you ensure that your dog gives them space.