It could very well be worn older hardware that has caused some issues yeah, drives in general to get worn, sometimes a retune can be done (for PC drives it would need to be disassembled to do that so maybe not) or a lens clean may also help
DVD discs though the quality does vary drasticly for DVD-R media so it is easy to get bad media and I do strongly recommend you try some DVD+R disc mostly for testing to see if your PS2 can handle those well as they are of a higher standard compared with DVD-R media but not all consoles can handle those and some users say that DVD+R's are no good for them, in general though DVD+R is better than DVD-R.
Some games will lag though no matter how well you burn them, that has more to do with PS2 hardware not being able to read -R/+R media as quickly as retail discs and the type of drivers those games use for FMV than your burning.
P.S. ever heard of ESR??? it lets you boot DVD games directly without need of SwapMagic and can be installed with SwapMagic
basically a bit of software on your memcard is ran.
ESR works with patched DVD based games, the patch and the software on the memcard makes the PS2 see the discs as DVD Video so the machine doesn't just say this is not PS2 disc, depending how you set up ESR that can either just auto boot the game or you can set a custom menu for the PS2 to include and short cut to manually run ESR, or you can set a short cut key on boot.
ESR also has a higher compat over SwapMagic and works fine with multi disc DVD games like XenoSaga 2 and 3.
ESR can also run Dual Layer discs but to be honest most PS2 hardware will struggle to run those so I still would say look for DVD5 rip kits.