Indeed GEOquery cannot give you the actual data as it could (given availability) for microarrays. Often authors of the study upload some sort of raw or normalized counts under "Supplement" in the GEO entry. If not you can check whether projects such as recount or BioJupies have the raw counts available. If not you need to download the fastq files and process manually.

For more details please elaborate more.

I would look into GEO2R https://www.ncbi.nlm.nih.gov/geo/geo2r/

You can check out our package phantasusLite. Not all RNA-seq datasets are available there, but it's a good percent. See the vignette here for the example: https://bioconductor.org/packages/release/bioc/vignettes/phantasusLite/inst/doc/phantasusLite-tutorial.html#loading-precomputed-rna-seq-counts

Also, if you're interested in human RNA-seq datasets, there is some efforts from GEO side to quantify RNA-seqs: https://www.ncbi.nlm.nih.gov/geo/info/rnaseqcounts.html I'm not aware of any R package wrapping this, but it should be relatively straightforward to download.