Having guys from top 10 pick aren't necessary.
You can have a team of Adam Morrison, Johny Flynn, Kwame Brown, Darius Miles and Ron Mercer and your team will still suck.
There's a difference between "necessary" and "sufficient." I think you mean the latter.
But as far as being "necessary" - yeah, you need top 10 picks. Most championship teams have several, and none have had zero.
What I mean by "necessary" is you don't need every starting 5 of your team to be drafted in the top 10. Just one or two is enough. San Antonio built a championship team where Duncan is the only guy drafted in the top 10.
No, it's not right to say "one or two is enough." Overall the Heat had eight. The Mavs had seven. The Lakers had four. The Celtics had three. The Pistons had four. The Heat team before that had six. Etc.
And these are not necessarily bench guys. The Heat's top 5 by minutes had 3-4 top 10 picks. Every single one of Dallas' top 5 by minutes was a top 10 pick. For the Lakers it was 3 of the top 6. For the Celtics, the top 3. And so on.
One's been "enough" twice in the last 40 years by my count.
To win championships you need top 20 players in the league, and the vast majority of those players are top 10 draft picks.
The Spurs are as always an exception, but they're just that. Their "one guy" was one of the most coveted #1 picks of the modern era, and has a good claim to being the best power forward ever. They won their first two rings with another #1 pick (and other top 10 picks). Then they reeled off the best streak of drafting in modern NBA history.
If what you're saying is "You can do it with one top 10 pick, but he has to be a #1 and one of the best players ever, and then you have to out-draft other teams by leaps and bounds," I'd agree. But that isn't really something from which you can generalize.