This is a double-red herring. First load factors do not correlate with cost, and second comparing the load factor of a nuclear power plant to a PV system is comparing apples with... not even oranges... more like comparing apples with seahorses. The interesting number would be: how much money did I have to put into that thing divided by how much MWh can I get out of a thing.
>life expectancy is 60-80 y against 20-30 years (x2-3)
Next red herring. If I buy a pair of shoes that last me 10 years but costs 200 bucks, that's 20 bucks/year. If I buy a pair of shoes that costs me 10 bucks and lasts one year, well, 10 bucks/year. Recycling/trashing a pair of shoes adds another 5 EUR/pair, so the cheap pair is 15/year and the expensive one is 20.5 EUR/year. The 10x higher life expectancy by itself does not mean shit to the annual cost.
The levelized cost of energy (LCOE) for nuclear in France (who are supposed to be doing nuclear really well) was 50 EUR/MWh in 2017, but that's with the state covering the insurance costs already, which are huge, so a massive hidden-in-plain-sight subsidy. (France EDF and IEA calculations). The Hinkley Point C project in the UK is about 100 EUR/MWh, which the state had to guarantee the operators, or else the operators would have dropped the entire project, probably because their analysts told them that the chances that their plant will be competitive on price over it's lifetime are slim to none.
On top of that, a longer life expectancy means a longer commitment, which can work in your favor, or against you.
The LCOE in 2018 for large-scale PV in Germany was 37-63 EUR/MWh. Onshore Wind 40-82, Offshore 75-138 (Fraunhofer). Prices are still dropping rapidly as both the technology and construction/maintenance requirements and processes improve, actually dropping, not just "estimated" drops. Prices for nuclear are said to drop too with new fancy technology, maybe... the nuclear lobby said... but so far that's pure speculation and e.g. the fancy EPR-type nuclear plants in France/UK for now actually do not show lower costs.
The US has PV at roughly 75 USD/MWh, and nuclear at roughly 96 USD/MWh.
I'd call the PV/Wind LCOE at the very least "competitive" to the LCOE of nuclear, sometimes already cheaper, and otherwise estimated to be cheaper soon.
Now, you got a point that switching to renewables requires additional and/or refined infrastructure, like changes to the power grid, energy storage/backup power plants, etc. which requires quite a bit of additional research and investment.