You never quantitatively defined what you consider "slow".

It is not the speed of your hiking but the total amount of hours needed to get a certain amount of miles that defines "slow". The biggest thing that slows you down is stopping. "Slow and steady" often ends up fast enough to reach your goal.

Do not let others determine your pace, or your goals. However, following an experienced hiker can sometimes help you understand how to pace yourself. When I started running, a coach paced me for a few days until I got the hang of it.

There is also a psychological "leader's advantage" when walking in a group. Most people feel "slow" or actually slow down when following, yet will speed up a bit when in the lead. On an obvious trail, I always put my slowest person at the head of the line.

If I accept a hiking partner, I feel it is my duty not to leave them in the dust. That simply is part of the responsibility of leading. If you have been abandoned in groups, you are hiking in the wrong group!