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I agreed to your opinion because having different trading pairs can put someone in a tight angle were it will be too hard for him or them to followup the trade as the market is waving, although this can depends on individuals because professional traders can have about more trading pairs, what I won't encourage is to trade on a newly launched altcoin as a newbies because they wouldn't know how to control and handle the market forces.
Don't assume that all traders have the same abilities, most traders who we don't know are still likely to make big profits with their trading approach. Even on newly listed meme coins or altcoins, they can still make profits although this method cannot be recommended for beginners.
Experienced and knowledgeable traders can always develop their trading skills and they can have a good plan for it. So I never think they are wrong in choosing trading pairs as long as they are able to do it and accept all the consequences.