The more teams the better in my opinion... although we don't want to see "no hopers" entering just to make up numbers - well no more than we have at the moment.. If a new team meets the entry requirements then they should be allowed to enter. Existing teams shouldn't be allowed to have any sort of veto in that area.
Otherwise we have a "franchise" situation where anyone that wants to compete in F1 has to buy an existing team.
And talking of "no hopers" it's been 13 years since the constuctors chamionship has been won by any team other than Red Bull or Mercedes.
And since McLaren won in 1998 we have seen only Ferrari, Renault and Brawn as winners in the other years.
Oh... we had 11 teams as recently as 2016 so the ten team "limit" is hardly a long standing thing.
We also need to consider who "owns" F1?
And who "calls the shots" on F1 is operated as a "sport"?
Yes, there should be more teams, there should be no limit or set number of teams, and anyone whose car and driver meets regulations should be allowed to participate, up to the limit of the individual track. I lament the loss of privateers in F1, as well as in NASCARE and "Indycar". Originally F1 was based on national teams in national colors - green for England, red for Italy, silver for Germany, blue for France, yellow for Spain, etc. - but by the fifties that was disappearing and it became primarily manufacturer teams, though still with strong national pride, then the small constructors and more privateers appeared ...an Italian driver in a German car wins, what nation did that represent? Then in the sixties sponsorship appeared and national colors were superseded by sponsor colors. Which brings us to:
"We also need to consider who "owns" F1?
And who "calls the shots" on F1 is operated as a "sport"?"
As with every professional sport today, it is owned by the sponsors. Once any sport accepts sponsorship money it relinquishes control of that sport, the sponsor now dictates the rules and regulations, the venues, the schedules. Doesn't matter the sport - soccer, hockey, football, basketball, baseball, auto racing, even Olympics - follow the money and you'll find who runs the show.
As I've elsewhere noted, Frank Williams was once asked if F1 is about business or racing and replied, "Formula One is a big business that happens to go racing every two weeks".
Mike Helton was asked if NASCARE would race on a new track recently opened and replied, "If they would like us to appear in their market...." (?? "appear in their market"?, what about "race on their track"?).
The Olympics, once staunch traditionalists of their sports, have besmirched their image with the likes of "Olympic Beach Volleyball" and "Olympic Skateboarding". All because that will attract more profits ...er, "viewers".
Ultimately once sponsorship is involved everything else becomes secondary to profit.
(But at least F1 has not been hit as badly as US motorsport. It is still just "Formula One Racing", not the "DHL F1 Series"; it still races at Monza and Silverstone, not at "Heineken Road Course" or "Pirelli Speedway"; the races are still the German Grand Prix and French GP, not "Rolex 200" or "Lenovo 300".)