Pagerank has had to change many times to combat black hat SEO and other undesirable outcomes. It is esp vulnerable to gaming the system. It has other problems

Pagerank has had to change many times to combat black hat SEO and other undesirable outcomes. It is esp vulnerable to gaming the system. It has other problems people have mentioned here. Do you want to wage a constant arms race with the exploiters? Is that really the best use of your time at a start up? Are you gonna expend the amount of resources Google expends on it and still doesn't get it perfect?