Doesn't meiosis form two pairs of similar cells and two pairs of opposite cells?
Great question - I think there are two misconceptions in your question that are interfering with your understanding.

First, crossing-over occurring at just the "tips" is just for clarity in textbooks so you can easily follow the different pieces of chromosome.

Although crossover events tend to occur at particular sequences, these don't have to be at the tips. There can also be multiple crossovers on the same chromosome, or none at all. See this link for some estimates of recombination rates for different species.

Second, gamete diversity doesn't depend only on crossing-over during meiosis, it also depends on the incorporation of just a single chromosome from each pair. Humans, for example, have 23 pairs of chromosomes. There are therefore 2^23 = 8388608 different combinations of chromosomes - with NO crossing over! Therefore, even without recombination, the odds of two genetically identical sperm fertilizing two genetically identical eggs are incredibly small.