Yes, altcoin season has started in usd or usdt pairs but if we analyse the btc pairs alts are still in downtrend so I would say that once the alts go bullish with respect to btc only then we can call it real alt season and yes I endorse your choice and I think ETH is the ultimate alt to hold.
The flagship of altcoins is ethereum and it will be possible to assume that the altcoin season is open only after ETH reaches its ATH. And now ethereum is literally one step away from its high and we can expect that it will reach it in the near future.