How fast or slow your play needs to be is determined by why you miss a ball. Did you miss the ball because of poor mechanics or was your pattern less than optimal? Usually when a good player misses after making a couple balls it is because he made a mistake earlier. The player saying you play to fast probably saw you making planning errors. Of course you have to consider the possibility he is wrong too, but a good chance he isn't. An observer often sees better than the person at the table.
When I was a teen I gambled with a man that was in his seventies, maybe eighties. Joe was very slow moving around the table, he shot so slow that the balls never lost contact with the bevel going in a pocket. Glaciers were speedburners compared to Joe. He could run out, and take fifteen minutes doing it without stalling. He was just that slow. The slower he seemed to play the faster I played. I sat on the edge of my chair or stool and jumped up as soon as he missed. In my rush I would miss a ball or blow shape then the torture began again. I wouldn't duck Joe but I gave him the money I had won from better players.
After several months of Joe beating me unmercifully I hit on a simple move. No more edge of the chair, I sat in the chair, leaned back, maybe propped a foot up. I watched Joe like a mildly interested observer. When he missed, I got up an ambled up to the table. Joe never beat me again. More importantly he taught me how to deal with slow players of all types. When people ask about mentors I always include Joe although he surely didn't mean to be one! It isn't exaggerating at all to say my dealings with Joe that cost me a few hundred and some pride made me thousands in the next seven or eight years. Any time somebody slow played me I would just sit deep in my chair, make a point of taking a swallow of beer when they missed, then get up slowly and go shoot.
Hu