Be appropriately direct.
Come right out with it. Tell your readers what you really mean.
Ban words and expressions such as, 'numerous', 'detrimental' and 'a number of...' They hide your meaning and invite questions: 'How numerous? How detrimental and in what way? What number?'
Instead you might write: 'We have received 25 enquiries so far.' You might drop the word detrimental and tell your readers what the effect will be, maybe, 'If we send too many staff out to meet customers, we won't have enough to answer telephone calls.' Try eliminating the expression, 'a number of...' and see if it makes any difference to the sentence.
Avoid passive writing
Passive writing is indirect too. My local supermarket has a sign next to the glassware, 'All breakages will be paid for'. I think that's very generous of them. Maybe, 'If you break it, we will ask you to pay for it.'
So what's appropriately direct? Your social skills will tell you.
A client once sent me a letter from a website designer who was doing some marketing. The designer told our client that the company's current website was visually bland and boring. The content, he said, was great, but the presentation was 'slack'. Our client agreed, but gave the upgrade to someone else.
If your tone seems harsh or accusing, soften it with a little less directness. Ask yourself what you would say to that person or group that would make your meaning clear, but not cause offence.