The "bigger problem" is that it is insufficient to observe the life carrying capacity of a planet for a few decades and conclude that it is stable long term.

For example, the host star could have variability measured in thousands or millions of years that would render the planet inhospitable to humans but not the indigenous life, which would have been adapted to these cycles.

Similarly, the planet could experience regular asteroid impacts due to passing through a recently broken up rock that intersects its orbital path.

Some of these risks can be eliminated through careful study, but this would require something like a century of painstaking geology, thorough astronomic surveys of its neighbourhood, a full fossil record, etc...