Retirement planning has some pretty straight forward aspects and some difficult to predict aspects. If you don’t save substantial amounts of money over a long period of time there is little hope for a good retirement nest egg (outside of things like winning the lottery or living off an inheritance). So consistent savings over a long period is normally a requirement. You can get decent estimates like saving 8% of your income from age 30 to age 65 (in a 401k, Roth IRA…) but how you investments perform during that period will have a large impact on your success (as will how much risk you want in retirement, the state of health care at that time, inflation, tax rates, your health insurance…).
This is a good article discussing some options as you close in on retirement and the financial picture become clearer: Two More Years for a Better Retirement. From Fidelity: Survey: One-Third of Americans Delaying Retirement.
One alternative to delaying retirement is to start saving more earlier but the overall data shows few are taking that option.