Ludia keeps messing up by “accident” allowing people to buy unlimited amounts of boost. A while back it was attack speed and for some others it was health and attack for a few lucky people it was both. So they rolled everything back and set a max number for people to buy and gave people money back. If people came to the forums, they knew it was not intended, and that is why it is considered an exploit.
So after the rollback, an option again came up to buy health and attack. It was supposed to be a limited supply, but people were still able to buy more.
The amount of effort to put into the game to level a creature from 24 on up, is rather long and complex. One boost in attack and one boost in speed. Is an equivalent to adding another level to a creature. Even at Tier 6,(64 boost burn rate) where you have to spend a bit of money, that is a bargain.
Many people have boosted their creatures to Tier 7 and above and are absolutely dominating everything and the match making system algorithm is somehow messed up by this.
At least the fixed the speed issue somewhat, by only allowing a limited purchase amount, but there might have been a chance, that was exploitable with a restart as well, and it was missed.